TK 

6550 
N53Y- 


Nilson 
Radio  questions  and  answers 


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RADIO 
QUESTIONS  AND  ANSWERS 


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RADIO 
QUESTIONS  AND  ANSWERS 

ON  GOVERNMENT  EXAMINATION 
FOR  RADIO  OPERATOR'S  LICENSE 


BY 

ARTHUR  R.  NILSON 

A88OC  .    MEM.    INSTITUTE    OP    RADIO    ENGINEERS,    DIRECTOR,    EAST   SIDE 
RADIO    SCHOOL,    153    EAST   86TH   STREET,    NEW   YORK   CITY 


SECOND  IMPRESSION 


McGRAW-HILL  BOOK  COMPANY,  INC. 
NEW  YORK:  370  SEVENTH  AVENUE 

LONDON :  6  &  8  BOUVERIE  ST.,  E.  C.  4 
1921 

32271 


COPYRIGHT,  1921,  BY  THE 
MCGRAW-HILL  BOOK  COMPANY,  INC. 


TK: 


PREFACE 

A)^:  This  book  is  written  especially  for  students  and  operators 
oJ  _i  who  are  about  to  take  the  government  examination  for  a 
/)  >L  Radio  Operator's  License. 

The  material  contained  herein  has  been  drawn  from  many 

'    sources,  carefully  chosen  and  compiled  from  the  commercial 

radio  operator's  standpoint.     While  the  reader  may  not  be 

f/     willing  to  accept  the  text  as  sufficient  in  all  points,  it  must 

*(    be  remembered  that  there  are  many  ways  of  answering 

%>    questions  and  as  all  viewpoints  cannot  be  taken  in  a  work 

of  this  kind,  the  one  considered  most  expedient  was  chosen. 

Q    It  is  assumed  that  the  reader  understands  radio  operating 

^    and  theory  completely  and  that  this  book  will  merely  serve 

to  bring  out  certain  salient  points  as  well  as  to  show  the 

J    general  form  of  answering  questions  of  this  kind. 

•^        In  conclusion  let  me  caution  all  applicants  who  take  the 

$*    Radio    Operator's    License    Examination    to    answer    all 

questions  fully,  never  using  etcetra  to  explain  a  meaning. 

Do  not  be  brief. 

A.  R.  N. 


CONTENTS 

PAGE 

PREFACE vii 

PART  I. — RADIO  AND  ELECTRICITY.     THEORETICAL 1 

PART  II. — TRANSMITTING  APPARATUS,  SPARK 7 

PART  III. — ARC  TRANSMITTERS 28 

PART  IV. — STORAGE  BATTERIES 33 

PARTY. — MOTORS  AND  GENERATORS 41 

PART  VI. — RECEIVING  APPARATUS 47 

PART  VII. — VACUUM  TUBES,  RECEIVING 61 

PART  VIII. — LAWS  AND  TRAFFIC  REGULATIONS 63 

PART  IX. — REGARDING  LICENSE  EXAMINATION 69 

PART  X. — ADDITIONAL  QUESTIONS  WITHOUT  ANSWERS 71 

ELECTRICAL  DEFINITIONS 77 

BIBLIOGRAPHY 80 

APPENDIX  1 82 

APPENDIX  II .84 


RADIO 
QUESTIONS  AND  ANSWERS 

Part  I 

RADIO  AND  ELECTRICAL 
THEORY  AND  PRACTICE 

Ques.  1.  What  effect  has  the  transmission  of  energy  by  a 
power  transformer  on  the  impressed  frequency? 

Ans.  None. 

Ques.  2.  Describe  the  following  properties : — Electromotive 
force,  current,  resistance,  watts  as  relating  to  the  D.  C.  cir- 
cuit. 

Ans.  Electromotive  Force,  abbreviated  E.M.F.,  is  the  term 
applied  to  electric  pressure  and  is  measured  in  volts. 

Current  is  defined  as  the  amount  of  electricity  passing  a 
given  point  in  unit  time  and  is  measured  in  amperes. 

Resistance  is  the  opposition  to  the  flow  of  current  shown 
by  every  D.C.  circuit.  It  is  measured  in  ohms. 

Watts  are  the  units  by  which  power  is  measured.  In  D.C. 
circuits  the  voltage  multiplied  by  the  amperes  flowing  in  the 
circuit  gives  watts.  When  figuring  the  watts  consumed  in  an 
A.C.  circuit  the  process  is,  volts  X  amperes  X  power  factor. 

Ques.  3.  What  is  meant  by  spark  frequency,  generator  fre- 
quency, wave  train  frequency? 

Ans.  By  Spark  Frequency  is  meant  the  number  of  sparks 
jumping  the  spark  gap  per  second.  It  is  dependent  upon  the 
generator  frequency.  In  modern  transmitters  properly  ad- 
justed, there  is  one  spark  per  alternation  of  the  A.C.  supply. 
For  example,  if  the  generator  delivers  500  cycles  per  second, 
the  spark  frequency  is  1000  per  second  or  in  other  words  a 
spark  discharges  across  the  spark  gap  1000  times  per  second. 
1 


RADIO  QUESTIONS  AND  ANSWEE 


Fig.  2.  Independent  Spark  Transmitter 
(Courtesy,  Independent  Wireless  Telegraph  Co.) 


RADIO  AND  ELECTRICAL  THEORY 


Fig.  3.  Independent  Are  Transmitter 
(Courtesy,  Independent  Wireless  Telegraph  Co.) 


4  RADIO  QUESTIONS  AND  ANSWERS 

Generator  Frequency  is  the  number  of  cycles  per  second  of 
the  electromotive  force  delivered  by  the  alternator.  The  fre- 
quency is  expressed  in  cycles  per  second. 

Wave  Train  Frequency  denotes  the  number  of  wave  trains 
or  groups  of  wave  trains  radiated  per  second  by  the  open 
radiating  or  antenna  circuit  of  a  radio  transmitter. 

Ques.  4.  Define  induction,  self  induction. 

Ans.  Induction  is  the  act  or  process  by  which  an  electrical 
conductor  or  a  magnetizable  body  becomes  itself  electrified  or 
magnetized  in  the  presence,  without  necessarily  actual  con- 
tact, of  an  electrically  charged  body,  a  magnet,  or  a  magnetic 
field  produced  by  an  electric  current. 

Changes  in  the  magnetic  field  surrounding  a  conductor  will 
induce  E.M.F.  in  the  circuit  itself.  This  is  called  self  induc- 
tion, provided  the  winding  in  question  produces  the  field. 

Ques.  5.  Has  an  undamped  wave  a  decrement? 

Ans.  It  has  zero  decrement. 

Ques.  6.  Four  condensers  of  .002  microfarads  are  con- 
nected in  series.  What  is  the  total  capacitance  1 

Ans.  The  formula  for  condensers  in  series  is 

i=J_     JL     J_     JL 

c~cl+c*+ct+ci 

which  applied  to  the  above  example  reads: 
^=^2+^2+^2+^2=^2  =  200°' 


-  microfarads. 

2000 

When  all  capacitance  values  are  alike  as  in  the  above  ex- 
ample the  total  capacitance  when  series  connection  is  used  is 
the  x;apacitance  of  one  condenser  divided  by  the  number  in 
the  bank. 

Ques.  7.  What  is  meant  by  a  broadly  tuned  circuit? 

Ans.  A  broadly  tuned  circuit  is  one  that  responds  (re- 
ceiver) or  transmits  (transmitter)  over  a  wide  range  of  wave- 


RADIO  AND  ELECTRICAL  THEORY  5 

lengths.  One  in  which  the  logarithmic  decrement  exceeds 
two-tenths. 

Ques.  8.  What  is  a  sharp  wave  ? 

Ans.  A  sharp  wave  is  one  in  which  the  logarithmic  decre- 
ment per  complete  oscillation  does  not  exceed  two-tenths. 


Fig.  4.  International  Receiver 
(Courtesy,  International  Radio  Telegraph  Co.) 

Ques.  9.  What  is  a  pure  wave? 

Ans.  A  pure  wave  is  the  radiated  wave  of  a  transmitter, 
the  character  of  which  is  such  that  it  radiates  two  or  more 
wavelengths,  the  shorter  wave  not  radiating  more  than  10 
per  cent  of  the  energy  radiated  by  the  desired  longer  wave. 

Ques.  10.  What  is  capacitance? 

Ans.  That  property  possessed  by  a  condenser  which  en- 
ables it  to  hold  a  charge  of  electricity  is  called  capacitance 
(capacity). 

Ques.  11.  What  is  the  effect  of  placing  a  condenser  in  ser- 
ies with  the  antenna,  and  under  what  conditions  is  it  neces- 
sary? 


6  EADIO  QUESTIONS  AND  ANSWERS 

Ans.  Placing  a  condenser  in  series  with  the  antenna  de- 
creases the  resulting  capacitance  and  consequently  the  wave- 
length. When  the  natural  wavelength  of  the  antenna  is 
higher  than  that  which  is  desired  the  wavelength  of  the  cir- 
cuit may  be  reduced  by  connecting  a  condenser  in  series. 
The  wavelength  may  be  reduced  nearly  to  one-half  by  this 
method  but  not  below  such  a  value  for  reasonable  efficiency. 
Any  decrease  below  the  natural  wavelength  tends  to  decrease 
efficiency. 


Part  II 
TRANSMITTING  APPARATUS,  SPARK 

Ques.  12.  How  do  you  increase  radiation  with  a  synchro- 
nous rotary  spark  transmitter? 

Ans.  If  the  primary  E.M.F.  to  the  step  up  power  trans- 
former is  fixed  the  radiation  in  the  open  oscillating  circuit 
of  a  transmitter  equipped  with  a  synchronous  rotary  spark 
gap  may  be  increased  by  carefully  manipulating  the  angu- 
lar adjustment  of  the  stationary  electrodes  and  varying  the 
coupling  between  the  open  and  closed  oscillating  circuits.  A 
variation  of  the  speed  of  the  motor  generator  will  also  effect 
the  radiation,  causing  it  to  increase  or  decrease  depending 
upon  various  conditions  in  the  apparatus.  "When  adjusting 
for  increased  radiation  the  antenna  ammeter  should  be  care- 
fully watched.  Increasing  the  input  to  the  power  trans- 
former will  usually  result  in  increased  radiation  on  any  type 
of  transmitter. 

Ques.  13.  How  may  the  radiation  of  a  quenched  gap  trans- 
mitter be  increased  ? 

Ans.  Generally  speaking,  the  radiation  of  a  quenched  gap 
transmitter  may  be  increased  by  increasing  the  number  of 
gap  units  in  use  and  carefully  varying  the  coupling  between 
the  open  and  closed  oscillating  circuits.  It  is,  of  course,  pos- 
sible to  use  too  many  units  of  the  quenched  gap  at  once,  there- 
by endangering  the  insulation  of  the  set  as  a  whole.  The  cor- 
rect number  for  maximum  radiation  with  a  particular  set 
may  best  be  found  by  experiment.  Increasing  the  input  to 
the  primary  of  the  power  transformer  will  increase  the  radia- 
7 


8  RADIO  QUESTIONS  AND  ANSWERS 

tion  but  care  must  be  taken  not  to  overload  the  set  by  using 
too  high  power. 

Ques.  14.  What  is  meant  by  ratio  of  transformation  of  the 
step  up  transformer  ? 

SYMBOLS 


CROSSED  WIRES, 

(nor  JOINED) 


JOINED  WIPES 


RESISTOR 

-mm 


INDUCTOR,  IKON  COP* 


MUTUAL  INDUCTANCE ,OK  INDUCTIVE  COUPLER 


LAMP  BANK 


ARC 


Fig.  5.  Standard  Symbols  I 


TRANSMITTING  APPARATUS 


Ans.  By  ratio  of  transformation  we  compare  the  primary 
input  volts  with  secondary  output  volts.     The  ratio  of  trans- 

I 


COIL  AERIAL 


JL 

THERMOELEMENT 


ENCLOSED   FUSE 


CIRCUIT 
BREAKER 


loo] 

PLUG  FUSE 


TWO  PHASE 
ALTERNATOR 


CRYSTAL  DETECTOR 


SHUNT    MOTOR 

r-'WV— 
SERIES  MOTOR. 


NON-SYNCHKONOUS 
GAP 


SYNCHRONOUS 
OAP 


Fig.  6.  Standard  Symbols  II 


formation  is  the  ratio  of  the  number  of  turns  of  wire  on  the 
secondary  to  the  number  of  turns  on  the  primary.     If,  for 


10  RADIO  QUESTIONS  AND  ANSWERS 

instance,  a  transformer  steps  up  the  voltage  from  100  volts 
to  5000  volts  the  ratio  of  transformation  would  be  50,  or  in 
other  words,  the  voltage  is  stepped  up  fifty  times.  Now  let 
us  assume  that  the  primary  of  the  transformer  has  400  turns. 
In  order  to  step  up  the  impressed  voltage  fifty  times  it  would 
be  necessary  to  have  fifty  times  as  many  turns  on  the  second- 
ary as  are  on  the  primary,  or  20,000  turns. 

Ques.  15.  Of  what  use  is  a  hot  wire  ammeter  in  a  trans- 
mitting circuit? 

Ans.  A  hot  wire  ammeter  is  used  to  indicate  resonance  be- 
tween the  open  and  closed  oscillating  circuits  and  also  indi- 
cates in  a  relative  way  the  energy  radiated  by  the  transmit- 
ting set.  In  modern  apparatus  the  hot  wire  ammeter  is  re- 
placed by  a  thermo-couple  electro-magnetic  ammeter  which 
is  called  the  antenna  ammeter  or  radio  frequency  ammeter. 

Ques.  16.  Of  what  use  is  an  antenna  timing  inductance 
in  connection  with  a  radio  transmitter? 

Ans.  The  antenna  tuning  inductance  or  loading  coil  as 
it  is  more  generally  termed  is  used  in  the  open  oscillating 
circuit  of  a  radio  transmitter  for  obtaining  wavelengths  be- 
yond the  range  of  the  oscillation  transformer  alone. 

Ques.  17.  What  effect  has  the  closed  circuit  of  a  trans- 
mitter upon  the  frequency? 

Ans.  The  closed  oscillatory  circuit  greatly  increases  the 
frequency  of  the  high  voltage  alternating  current  supplied 
from  the  secondary  of  the  step  up  transformer.  This  is  neces- 
sary in  order  to  produce  ether  waves  to  travel  over  long  dis- 
tances. In  any  spark  transmitter  the  closed  circuit  may,  for 
example,  increase  the  frequency  as  high  as  600,000  or  more 
cycles  per  second. 

Ques.  18.  Where  are  the  protective  condensers  usually  lo- 
cated in  transmitting  apparatus  ?  Explain  fully,  giving  their 
purpose. 


TRANSMITTING  APPARATUS 


11 


Fig.  7.  International  Panel 
(Courtesy,  International  Radio  Telegraph  Co.) 


12 


RADIO  QUESTIONS  AND  ANSWERS 


Ans.  Protective  condensers  are  installed   as  indicated  in 
the  diagram  figure  43  : 

(1)  Across    terminals    of    primary    of    power    transformer. 

(2)  Across    terminals    of    armature    of    alternator. 

(3)  Across    terminals    of    field    of    alternator. 

(4)  Terminals   of   shunt   field    of   motor. 

Protective  devices  are  also  placed  across  the  terminals  of  the 
armature  of  blower  motor  on  a  quenched  gap  set.     The  pur- 


Fig.   8.    Dubilier   Protective   Condenser 

pose  of  the  protective  device  is  to  protect  the  apparatus  to 
which  they  are  connected  from  puncture  of  insulation,  should 
a  high  voltage  kickback  occur  from  the  high  frequency  cir- 
cuits. A  photograph  of  one  of  the  latest  type  protective 
condensers  is  shown  in  figure  8. 

Ques.  19.  Describe  fully  how  you  would  proceed  to  ad- 
just a  spark  transmitter  to  a  given  wavelength. 

Ans.  It  is  well  to  remember  in  answering  a  question  of  this 
kind  that  a  spark  transmitter  of  the  types  commonly  used 


TRANSMITTING  APPARATUS  13 

today  have  two  independent  circuits,  namely;  the  closed  os- 
cillating circuit  consisting  of  the  condensers  (capacitance), 
the  primary  turns  of  the  oscillation  transformer  (inductance) 
and  the  spark  gap ;  and  the  open  oscillating  circuit  consist- 
ing of  the  secondary  of  the  oscillation  transformer,  antenna 
tuning  inductance  (loading  coil)  radio  frequency  ammeter, 
antenna  and  ground.  A  variation  of  the  capacitance  or  in- 
ductance value  in  either  of  these  circuits  affects  the  radiated 
wave.  First,  tune  the  closed  circuit  to  the  desired  wave- 
length by  closing  the  key  and  causing  the  spark  to  jump  the 
gap.  Situate  the  wavemeter  in  inductive  relation  to  the  cir- 
cuit and  take  a  reading.  Resonance  on  the  wavemeter  will  be 
indicated,  according  to  the  type  of  wavemeter  used,  by  a 
maximum  sound  in  the  telephone,  a  maximum  reading  of  a 
current  reading  meter  or  the  brightness  of  a  glow  lamp. 
Whichever  device  is  used  resonance  will  be  indicated  by  a 
maximum  indication. 

If  the  wavelength  reads  high  reduce  the  number  of  turns 
of  inductance,  if  too  low  increase  the  inductance  by  adding 
turns.  It  is  not  necessary  to  adjust  the  capacitance  (con- 
densers) as  this  is  fixed  at  the  factory.  However,  for  three 
hundred  meters  a  switching  or  plugging  arrangement  cuts 
down  the  value  of  the  capacitance  automatically  and  this 
switch  or  plug  must  be  in  the  proper  position. 

While  it  is  not  absolutely  necessary,  it  is  always  best  when 
calibrating  the  closed  circuit  that  all  of  the  various. pieces 
of  apparatus  comprising  the  open  circuit  be  disconnected  one 
from  the  other  and  the  secondary  drawn  away  from  the  prim- 
ary coil  to  the  position  of  minimum  coupling.  This  is  so 
that  minimum  mutual  induction  will  take  place  between  the 
circuits  thereby  eliminating  any  broadening  effect  of  the 
measured  wave. 

When  the  closed  circuit  has  been  tuned  to  the  given  wave- 
length the  open  circuit  is  reconnected  and  the  coils  of  the 


14  EADIO  QUESTIONS  AND  ANSWERS 

oscillation  transformer  (coupler)  brought  in  close  relation. 
Inductance  is  then  added  or  subtracted  from  the  secondary 
or  antenna  inductance  (open  circuit)  until  the  antenna  am- 
meter indicates  resonance  by  a  maximum  indication.  This 
shows  that  the  open  circuit  is  now  tuned  to  the  same  wave- 
length as  the  closed  circuit  and  the  set  ready  for  operation. 

However,  in  order  that  the  purity  and  sharpness  of  the 
wave  may  be  checked  up  the  radiated  wave  should  be  meas- 
ured while  the  transmitter  is  in  actual  operation.  If  two  or 
more  waves  are  present  the  coupling  and  inductance  values 
of  the  secondary  and  antenna  loading  coil  should  be  so  pro- 
portioned that  the  energy  in  any  of  the  lesser  waves  shall  not 
exceed  ten  per  cent  of  the  energy  in  the  desired  wave. 

A  decrement  reading  should  then  be  taken.  According 
to  the  law  the  decrement  must  not  exceed  two-tenths  for  ordi- 
nary operation.  In  view  of  the  fact  that  it  is  not  necessary 
to  measure  for  decrement  to  tune  a  set  to  a  desired  wave- 
length, an  explanation  of  this  operation  is  omitted  in  this 
answer. 

Ques.  20.  Describe  an  oscillation  transformer.  What  im- 
mediate advantage  is  obtained  from  employing  such  a  device  ? 

Ans.  An  oscillation  transformer  is  shown  in  figure  9  and 
may  consist  of  two  spirally  wound  coils  one  of  which  is  the 
primary  and  the  other  the  secondary.  The  primary  con- 
sists of  from  seven  to  fifteen  turns  of  heavy  copper  conductor 
and  the  secondary  coil  consists  of  from  five  to  eight  turns 
of  conductor  having  the  same  large  surface  area  as  that  of 
the  primary  coil. 

An  oscillation  transformer  is  useful  because  it  allows  a 
very  flexible  degree  of  coupling  between  the  open  and  closed 
oscillating  circuits  with  no  direct  conduction  of  energy  from 
one  circuit  to  the  other.  This  makes  it  possible  to  adjust  for 
a  wave  of  low  decrement  as  well  as  for  a  pure  wave.  When 
using  an  oscillation  transformer  the  resistance  of  the  spark 


TRANSMITTING  APPARATUS  15 

gap  is  not  in  the  antenna  circuit.  This,  of  course,  also  tends 
to  keep  down  the  decrement  of  the  radiated  wave.  It  is  some- 
times the  practice  to  decrease  the  coupling  of  the  oscillation 
transformer  when  it  is  desired  to  decrease  power  transmitted 


Fig.  9.  Oscillation  Transformer 
(Courtesy,  International  Radio  Telegraph  Co.) 

but  with  the  newer  types  of  apparatus  this  method  is  obso- 
lete. 

Ques.  21.  What  are  the  principle  losses  in  a  power  trans- 
former ? 

Ans.  One  of  the  losses  that  takes  place  in  a  power  trans- 
former is  the  heat  loss  which  is  the  result  of  eddy  currents 


16  RADIO  QUESTIONS  AND  ANSWEES 

and  the  effect  known  as  hysterisis  in  the  iron  core.  To  lessen 
this  loss,  transformer  cores  are  built  up  of  laminated  soft 
iron  strips  each  strip  having  a  coat  of  insulating  shellac  or 
japan  applied  before  assembly  into  the  final  form.  There  is 
also  a  loss  in  the  windings  called  the  copper  loss. 

Ques.  22.  Describe  some  form  of  impact  excitation  trans- 
mitter. 


Fig.  10.   Cutting  &  Washington  Transmitter 

Ans.  A  modern  commercial  type  of  impact  excitation 
transmitter  is  shown  in  figure  10.  The  wiring  diagram  is 
shown  in  figure  11. 

Motor  Generator.  The  motor  is  connected  to  the  regular 
source  of  B.C.  supply  and  the  alternator  delivers  250  volts 
at  500  cycles  frequency. 

Transformer.  The  transformer  is  a  highly  efficient  one, 
of  the  closed  core  type  wound  as  an  auto  transformer  with  a 
ratio  of  5.6 :1  and  has  practically  no  leakage. 

Condenser  and  Primary  Inductance.  The  total  capaci- 
tance of  the  condenser  on  the  %  K.W.  set  is  .16  mfds.,  this 
is  automatically  decreased  when  using  300  meters,  and  the 
inductance  value  is  approximately  1.2  microhenries.  This 


TRANSMITTING  APPARATUS 


17 


18  RADIO  QUESTIONS  AND  ANSWERS 

shows  that  the  ratio  of  capacitance  to  inductance  in  an  im- 
pact excitation  transmitter  is  high.  This  fact  is  one  of  the 
chief  characteristics  necessary  to  get  impact  or  shock  excita- 
tion. 

Spark  Gap.  The  spark  gap  used  with  this  type  of  trans- 
mitter consists  of  two  electrodes  each  made  of  a  sparking  sur- 
face of  thin  tungsten  welded  to  copper  backs  and  operates  in 
air.  The  gaps  have  a  micrometer  adjustment  and  the  spark- 
ing distance  may  be  varied  by  the  thousandth  part  of  an 
inch.  The  gaps  are  provided  with  cooling  fins  and  locking 
nuts. 

Concentration  Circuit.  The  function  of  the  concentration 
circuit  is  to  concentrate  the  discharges  into  definite  groups 
so  that  the  oscillations  upon  which  the  tone  is  dependent  will 
have  approximately  equal  periods  of  activity  and  inactivity, 
thus  giving  maximum  telephone  efficiency. 

Oscillation  Transformer.  The  primary  consists  of  a  single 
turn  of  copper  tubing  and  has  an  inductance  value  of  1.2 
microhenries  as  explained  before.  The  secondary  consists  of 
30  turns  of  edgewise  wound  strip  having  a  total  inductance 
value  of  320  microhenries.  The  amount  of  inductance  in  use, 
however,  will  depend  upon  the  size  of  the  antenna. 

The  term  oscillation  transformer  as  applied  to  impact  ex- 
citation transmitters  is  in  itself  questionable  as  there  are 
no  oscillations  in  the  primary  circuit. 

A  wave  changing  switch  is  also  attached  which  is  used  for 
changing  the  wavelength  from  300  to  600  meters  and  which 
automatically  connects  in  the  proper  value  of  capacitance 
and  inductance. 

Theoretical  Operation.  The  condenser  charges  up  to  a 
potential  sufficient  to  break  down  the  gap  and  discharge 
through  the  gap.  Owing  to  the  low  persistence  of  the  prim- 
ary circuit,  the  non-volatile  nature  of  the  electrodes,  the  ratio 
of  periods  between  the  primary  and  secondary  circuits  and 


TRANSMITTING  APPARATUS  19 

the  pressure-wave  generated  due  to  the  viscosity  of  the  gas 
this  discharge  consists  of  only  a  half  cycle.  This  half  cycle 
sets  the  antenna  in  oscillation.  The  condenser  then  recharges 
and  when  it  has  reached  a  potential  almost  sufficient  to  break 
down  the  gap  the  back  E.M.F.  from  the  still  oscillating  anten- 
na adds  an  increment  to  the  voltage  across  the  gap  sufficient 
to  break  the  gap  down  so  that  this  second  discharge  comes 
in  the  proper  phase  to  increase  the  amplitude  of  the  antenna 
oscillations.  This  process  continues  throughout  approxi- 
mately the  middle  third  of  each  pulse  of  the  charging 


-Httt-Jfti'--^ 


Seconbldry 


Fig.    12.    Impact   Oscillations   Curve 

current.  Figure  12  gives  a  fundamental  idea  of  the  oscilla- 
tions in  the  primary  and  secondary  circuits  and  shows  that 
there  is  no  appreciable  reaction  between  the  circuits. 

A  set  of  the  above  description  can  be  tuned  very  quickly 
and  radiates  a  pure  and  sharp  wave  of  pleasing  tone  char- 
acteristics. 

Ques.  23.  What  is  the  difference  between  an  impulse  and 
an  impact  excitation  transmitter? 

Ans.  According  to  the  latest  standardization  report  of  the 
Institute  of  Radio  Engineers  impulse  excitation  is  a  term 
applied  to  any  type  of  transmitter  in  which  the  oscillations  of 
the  primary  circuit  are  rapidly  damped  out  and  the  second- 
ary allowed  to  oscillate  freely  in  its  own  natural  period  with- 
out any  appreciable  reactance  between  the  circuits. 

Impact  or  shock  excitation  on  the  other  hand  means  that 
the  gap  quenches  out  the  oscillations  of  the  primary  before 


20  RADIO  QUESTIONS  AND  ANSWERS 

one  or  two  half  cycles  of  oscillation  have  taken  place.  There- 
fore, any  well-designed  quenched  gap  transmitter  might  be 
termed  an  impulse  excitation  transmitter  whereas  "Impact 
Excitation"  would  imply  such  a  designed  set  as  described 
in  this  paragraph. 

Ques.  24.    What  is  meant  by  impact  excitation? 

Ans.  This  phenomenon  is  also  termed  impulse  and  shock 
excitation  and  designates  a  method  of  producing  free  alter- 


Fig.  13.     Roister  Dccremeter 

nating  currents  in  an  excited  circuit  in  which  the  duration 
of  the  exciting  current  is  short  compared  with  the  duration 
of  the  excited  current.  In  a  circuit  in  which  such  excita- 
tion is  taking  place  there  is  very  little  reaction  between  the 
circuits. 

Ques.  25.    Describe  a  form  of  decremeter.     Give  diagram 
and  operation. 


TRANSMITTING  APPARATUS 


21 


Ans.  A  photograph  of  the  latest  type  direct  reading  Kol- 
ster  decrement  is  shown  in  figure  13  and  the  diagram  of  con- 
nections is  shown  in  figure  14  below. 

Description.  The  decremeter  consists  of  a  single  turn  coil 
I,  which  is  connected  in  series  with  the  circuit  to  be  meas- 
ured. The  inductance  value  of  this  coil  is  so  low  as  to  be  neg- 
ligible. Coil  L  is  placed  in  inductive  relation  to  coil  I  and  is 
the  inductance  of  the  decremeter  circuit.  It  is  important 


Fig.  14.  Wiring  diagram  Kolster  decremeter 


that  the  coupling  between  coils  L  and  I  be  at  a  minimum 
coupling  position  when  the  decremeter  is  in  use.  Cv  is  a 
variable  condenser  to  which  is  attached  the  decremeter  scale 
through  gears.  A  small  condenser  marked  C£  is  fixed  in 
value  after  proper  adjustment  and  is  placed  in  parallel  with 


An  indicating  meter  is  represented  by  H.  The  scale  of  the 
meter  is  so  marked  that  the  readings  are  proportional  to  the 
square  of  the  current  measured. 

If  it  is  desired  to  measure  the  wavelength  of  distant  sta- 
tions the  crystal  detector  D  and  head  telephones  T  may  be 
used  to  indicate  resonance. 


22  RADIO  QUESTIONS  AND  ANSWERS 

The  decremeter  may  be  used  for  calibration  purposes  by 
using  the  buzzer  provided  and  which  is  indicated  in  the  cir- 
cuit as  R.B. 

Operation.  To  measure  the  decrement  of  an  oscillating 
circuit  connect  coil  I  in  series  with  the  circuit  to  be  measured 
as  indicated  in  the  diagram.  Then  rotate  the  condenser  to 
the  position  of  resonance  as  indicated  by  a  maximum  reading 
on  the  current  meter.  The  maximum  reading  is  then  reduced 
to  one-half  its  value  by  rotating  the  condenser  towards 
the  minimum  or  maximum  ends  of  its  scale.  The  next 
operation  is  to  set  the  decrement  scale  at  zero  and  clamp 
it  so  that  when  the  condenser  scale  is  again  rotated  it  will 
rotate  with  it.  The  condenser  is  then  rotated  back  until  the 
current  meter  reading  rises  from  one-half  maximum  to  maxi- 
mum and  back  to  one-half  maximum.  The  reading  now  op- 
posite zero  on  the  decrement  scale  is  the  sum  of  the  decre- 
ments of  the  circuit  under  measurement  and  the  decremeter 
decrement.  By  subtracting  the  latter  decrement,  which  is 
given  on  a  chart  supplied  with  the  decremeter,  from  the  sum 
of  the  decrements  given  on  the  decremeter  scale,  the  decre- 
ment of  the  circuit  under  measurement  can  be  readily  ob- 
tained. 

Ques.  26.  How  would  the  high  potential  condensers  of  a 
transmitting  set  be  protected  from  puncture? 

Ans.  Connecting  condensers  in  series  divides  the  voltage 
between  them.  It  also  decreases  the  capacitance.  It  is  pos- 
sible then  to  protect  high  potential  condensers  by  connecting 
several  units  in  series,  but  in  order  to  maintain  the  total  ca- 
pacitance at  a  given  value  it  is  necessary  to  connect  an  equal 
number  of  such  groups  in  parallel.  Therefore,  the  series  par- 
allel connection  as  shown  in  figure  15  is  used. 

Another  method  to  protect  high  potential  condensers  from 
puncture  is  to  fit  the  unit  with  a  safety  spark  gap,  figure  16, 
which  is  set  just  below  the  puncture  voltage.  This  affords 


TRANSMITTING  APPARATUS 


23 


a  path  for  the  current  to  take  should  that  overload  value  be 
reached  and  therefore  no  damage  is  done  to  the  condenser. 
Ques.  26a.    What  is  the  electrical  function  of  the  closed  core 
transformer  ? 

I II II II 1 

HHHH 

Fig.  15,   Series  Parallel  Condenser  Hookup 

Ans.  The  closed  core  transformer  steps  up  the  low  volt- 
age, low  frequency,  alternating  current  obtained  from  the 
motor-generator  to  a  high  voltage  current  of  the  same  fre- 
quency which  is  necessary  to  charge  the  primary  condenser 
in  the  closed  oscillating  circuit.  The  condenser  discharges 
through  the  spark  gap,  causing  the  circuit  to  oscillate  at 
radio  frequency.  It  is  necessary  to  have  a  comparatively 
high  frequency  current  to  generate  ether  waves. 


^-Terminals  Connected-* 
to  Protected  Apparatus 

Fig.  16.  Protective  Spark  Gap 

Ques.  27.    What  are  three  ways  in  which  resonance  may 
be  indicated  on  a  wavemeter?     Draw  diagrams. 
Ans.     Resonance  may  be  indicated  by : 

a.  Telephone  receiver  and  detector. 

b.  Current  square  meter. 

c.  Glow  lamp. 

See  figure  17. 


24 


RADIO  QUESTIONS  AND  ANSWERS 


Ques.  28.  Draw  a  wavemeter  with  headphones  and  detec- 
tor connected  unilateraly. 

Ans.  This  is  shown  in  diagram  of  the  Kolster  decremeter, 
figure  14. 


(T>  A>  /T> 

i.s  |  Jig  _k 

k>   7-  T     k>  7p  >o  7p 

io   /  F>  '       k>  7 


(w) 

be 
Fig.   17.  Wavemeter,  methods  of  resonance 

Ques.  29.  Is  it  preferable  to  connect  the  condenser  across 
the  secondary  of  the  transformer  as  in  A  instead  of  as  in  B 
of  the  figure  18. 

There  is  no  difference  in  practice  between  these  circuits 
since  the  inductance  of  the  oscillation  transformer  is  negli- 
gible to  low  frequencies  allowing  the  condenser  in  both  cases 
A  and  B  to  receive  a  like  charge  and  since  during  discharge 
through  the  gap  the  inductance  of  the  pOAver  transformer  is 
a  complete  choke  to  the  radio  frequencies.  Both  methods  of 
connection  are  used  in  commercial  practice. 


A  B 

Fig.   18.    Condenser   to   Transformer   Connection 

Ques.  30.  Explain  in  detail  what  would  happen  if  one  or 
more  condensers  were  removed  from  the  closed  circuit  of  a 
transmitter. 

Ans.  The  wavelength  of  the  closed  circuit  depends,  as  does 
any  other  circuit,  upon  the  capacitance  and  inductance  in  the 


TEANSMITTING  APPARATUS  25 

circuit.  Therefore  if  one  or  more  condensers  (capacitance) 
were  removed  the  wavelength  would  be  reduced  accordingly. 
The  resonance  of  the  circuit  would  also  be  effected. 

Ques.  31.  What  are  the  four  main  circuits  of  a  spark 
transmitter  ? 

Ans.  1.  Low  frequency,  low  potential  circuit  consisting  of ; 
all  apparatus  from  A.C.  generator  to  primary  of  power  trans- 
former. 

2.  Low   frequency,    high   potential   circuit   consisting    of; 
secondary  of  power  transformer  and  condensers. 

3.  High  frequency,  high  potential  closed  oscillatory  cir- 
cuit.    It  consists  of  the  condensers,  spark  gap,  and  primary 
of  oscillation  transformer. 

4.  High  frequency,    high   potential   open   oscillatory   cir- 
cuit.    It  consists  of  antenna,  loading  inductance,  secondary 
oscillation  transformer,  and  ground. 

Ques.  32.    Describe  a  frequency  meter. 

Ans.  A  widely  used  frequency  meter  is  the  Hartman  and 
Braun  vibrating-reed  type.  It  consists  essentially  of  an  elec- 
tromagnet in  front  of  which  is  fixed  a  series  of  reeds  tuned 
to  given  frequencies.  When  an  alternating  current  flows 
through  the  magnet,  the  reed  tuned  to  that  frequency  vi- 
brates. A  scale  is  arranged  so  that  the  frequency  which  a 
given  reed  indicates  may  be  read  directly. 

Ques.  33.  Explain  the  action,  in  the  closed  oscillatory  cir- 
cuit of  a  transmitter,  when  the  key  is  pressed. 

Ans.  When  the  key  is  pressed  current  flows  from  the 
A.C.  generator  through  the  primary  of  the  step  up  power 
transformer  setting  up  a  magnetic  field  around  it.  The  ris- 
ing and  falling  of  the  magnetic  lines  of  the  primary  cut  the 
secondary  windings  inducing  an  E.M.F.  therein  and  raising 
it  to  a  very  high  voltage.  The  high  potential  condensers  are 
charged  to  the  break-down  potential  of  the  gap,  resulting  in 
a  discharge.  The  circuit  through  which  the  discharge  takes 


26  RADIO  QUESTIONS  AND  A 

place,  having  capacitance  and  inductance,  has  oscillatory 
characteristics  and  the  spark  discharging  through  it  sets  up 
oscillations.  The  spark  oscillations  in  turn  have  a  wave- 
length depending  upon  the  capacitance  and  inductance  of  the 
closed  circuit.  The  oscillations  in  the  closed  circuit  induce 
oscillations  in  the  open  oscillating  circuit  at  the  wavelength 
to  which  this  circuit  is  tuned.  The  oscillations  in  the  open 
circuit  are  radiated  out  into  the  ether  in  the  form  of  electro- 
magnetic waves. 

Ques.  34.  Describe  the  open  and  closed  core  transformer. 

Ans.  An  open-core  transformer  has  a  core  made  of  soft 
iron  in  strip  or  wire  form.  To  decrease  losses  the  individual 
wires  or  strips  that  constitute  the  core  are  shellaced.  An 
insulation  wrapping  is  wound  around  the  core  and  the  pri- 
mary winding  of  a  comparatively  few  heavy  turns  is  wound 
around  it.  A  heavy  insulation  is  placed  over  this  winding 
and  the  secondary  winding  of  many  turns  of  fine  wire  is 
wound  thereon  in  pan-cake  form.  The  path  of  the  magnetic 
field  in  an  open  core  transformer  is  open  as  will  be  seen  by 
referring  to  the  upper  transformer  figure  on  page  8.  It 
is  seen  that  the  field  path  is  completed  through  the  air. 

The  closed-core  transformer  is  shown  below  the  open  core 
figure  on  page  eight.  The  core  of  this  type  takes  the  form 
shown  in  the  figure  and  may  be  built  up  in  the  same  way  ex- 
plained for  the  open  core  type.  The  windings  are  also  of 
similar  characteristics.  The  magnetic  field  path  is  closed 
through  the  core,  hence  the  name  closed-core  transformer. 

Ques.  35.  Show  by  diagram  how  an  antenna  may  be  tested 
for  grounds. 

Ans.  Ground  leaks  in  antenna  insulation  may  be  detected 
by  connecting  a  voltmeter  in  series  with  antenna  and  apply- 
ing a  110-volt  current  as  shown  in  the  diagram  on  the  next 
page.  If  no  deflection  is  shown  by  the  meter  the  insula- 
tion is  good,  if  the  meter  indicates  a  flow  of  current  (de 


TRANSMITTING  APPARATUS  27 

fleets),  the  insulation  is  faulty  and  should  be  remedied.  A 
practical  method  used  by  radio-operators  and  inspectors  on 
shipboard  is  to  transmit  on  full  power  and  watch  closely  for 
arcing  in  the  antenna  circuit  and  antenna  proper.  The  radi- 
ation ammeter  will  not  register  if  the  antenna  is  badly 
grounded. 


/I0  V.Line        To  Test  Antenna 
Insulation 


Part  III 
ARC  TRANSMITTERS 

Ques.  36.  How  would  you  proceed  to  place  an  arc  trans- 
mitter in  operation  ?  Explain  fully. 

Ans.  To  place  an  arc  transmitter  in  operation  it  is  import- 
ant to  see  that  the  alcohol  cup  is  full  and  that  it  feeds  prop- 
erly. The  water  tank  should  be  about  three-quarters  full 
with  fresh  water  and  all  valves  opened.  Notice  should  be 
taken  that  the  water  circulates  properly  when  the  pump  is 
started.  To  start  transmitting,  the  following  operations 
should  be  gone  through  in  their  regular  order,  viz.: 

1.  Close  set  supply  switch. 

2.  Throw  changeover  switch  to  transmitting  position.  Note 
that  pump  is  started  and  that  carbon  electrode  is  rotating. 

3.  Start  motor    generator    by    closing    main-line    circuit 
breaker  and  bringing  motor  slowly  up  to  full  speed  with 
starting  rheostat.     Adjust  generator  voltage  to  about  250 
volts  by  adjusting  field  rheostat. 

4.  Start  alcohol  dripping  rather  rapidly.    Bring  electrodes 
about  1-32  inch  from  each  other. 

5.  Close  the  arc  main-line  switch  and  strike  the  arc.   Care- 
fully adjust  for  maximum  arc  length  without  causing  the 
arc  to  break.    It  will  be  necessary  to  allow  a  sufficient  amount 
of  alcohol  to  decompose  and  give  a  hydrogen  atmosphere  so 
that  the  arc  will  burn  steadily.    For  this  reason  do  not  draw 
out  the  arc  for  one  or  two  minutes  the  first  time  the  set  is 
started.    When  the  radio-frequency  ammeter  starts  reading, 
it  indicates  that  the  arc  is  oscillating  and  the  arc  starting 
resistor  switch  should  be  closed  and  the  arc  adjusted  for 


ABC  TBANSMITTEES  29 

maximum  radiation.  The  alcohol  feed  may  now  be  slowed 
down  and  only  enough  alcohol  allowed  to  drip  to  maintain 
maximum  radiation.  Signals  may  now  be  sent  by  manipu- 
lation of  the  telegraph  key. 

Ques.  37.  Draw  an  elementary  diagram  of  an  arc  trans- 
mitter, including  source  of  power. 

Ans.  See  figure  19  below. 

Ques.  38.  Of  what  material  are  the  negative  and  positive 
electrodes  made? 


Loading 

Inducfance 

Combined  Choke  Coil 


/Antenna 
Loading  oj 
Inducfance  <p) 

•and  Arc  Magnet  Winding 


Key 
Compensating  Loop 


— 1—  Ground 
Fig.  19.  Elementary  Are  Transmitter  from  Rource  of  Power 

Ans.  The  positive  electrode  is  made  of  copper  and  the  nega- 
tive electrode  is  made  of  carbon. 

Ques.  39.   Why  is  the  negative  electrode  slowly  rotated? 

Ans.  This  is  done  so  that  the  carbon  material  of  which 
the  electrode  is  made  will  burn  evenly. 

Ques.  40.  What  means  are  provided  for  keeping  the  elec- 
trodes of  an  arc  transmitter  cool  ?  Explain  fully. 

Ans.  The  copper  electrode  is  hollow  and  water  is  circu- 
lated through  it.  The  arc  chamber  is  also  provided  with  an 
exhaust  path  for  allowing  the  carbonized  hydrogen  gas  in  the 
arc  chamber  to  escape.  These  characteristics  in  the  design  of 
the  arc  tend  to  keep  the  electrodes  cool. 

Ques.  41.   Explain  two  ways  of  cooling  an  arc. 

Ans.    This  is  explained  in  the  above  question. 


30  RADIO  QUESTIONS  AND  ANSWERS 

Ques.  42.  Explain  how  to  obtain  maximum  voltage  across 
the  arc. 

Ans.  This  is  accomplished  by  carefully  adjusting  the  arc 
length  and  voltage,  by  turning  the  electrode  adjusting  handle 
and  by  means  of  the  field  rheostat.  It  is  also  necessary  that 
the  electrodes  be  in  good  condition. 

Ques.  43.  Describe  the  construction  of  the  positive  elec- 
trode of  the  arc. 

Ans.  The  positive  electrode  of  the  arc  is  copper.  It  con- 
sists of  a  copper  tip  which  is  fastened  to  a  brass  holder.  It 
can  be  removed  from  the  holder  when  it  has  burned  low.  The 
tip  is  so  constructed  that  water  can  flow  through  it,  thereby 

r  Conner 


r  wfy/rr  .^Dra&S  ri 


Fig.  20.  Positive  Electrode,  Are 

keeping  it  cool.  The  figure  20  shows  the  water  circulation 
and  general  construction  of  the  positive  electrode. 

Ques.  44.  How  would  you  adjust  the  flow  of  water  to  the 
cooling  chamber? 

Ans.  The  flow  of  water  can  be  adjusted  by  regulating  a 
valve  near  the  water  tank. 

Ques.  45.   What  is  an  arc? 

Ans.  The  Committee  on  Standardization,  Institute  of 
Radio  Engineers,  defines  the  arc  as  the  passage  of  an  electric 
current  of  relatively  high  density  through  a  gas  or  vapor,  the 
conductivity  of  which  is  mainly  due  to  the  electron  emission 
from  the  self-heated  cathode.  Under  present  practical  con- 
ditions, the  phenomena  takes  place  near  atmospheric  pres- 
sure. A  transmitting  system  using  an  arc  for  producing  the 
undamped  oscillations  is  sometimes  referred  to  as  an  "arc" 
or  an  arc  set. 


ARC  TRANSMITTERS 


31 


Ques.  46.  Of  what  materials  are  the  electrodes  in  an  arc 
transmitter  composed? 

Ans.  The  positive  electrode  is  made  of  copper  and  the 
negative  electrode  is  carbon. 

Ques.  47.  Draw  an  elementary  diagram  of  an  arc  trans- 
mitter. Explain  fully  its  operation. 

Ans.  For  elementary  diagram  of  arc  see  Fig.  21. 


An+enna 


Ground 
Fig.  21.  Fundamental  Arc  Transmitter 

The  arc  is  fed  by  a  direct  current  varying  in  pressure  from 
200  to  1200  volts,  depending  upon  its  size.  To  this  source  of 
supply  is  connected  the  arc  converter  where  the  supply  cur- 
rent is  converted  into  high  frequency,  undamped  etheral 
oscillations  in  the  following  manner. 

a.  The  arc  is  struck  and  the  high  potential  current  across 
the  terminals  begins  to  charge  the  condenser.  Therefore,  the 
condenser  takes  some  of  the  current  away  from  the  arc  and 
the  voltage  across  the  arc  increases  until  the  condenser  is 
fully  charged. 

&.  When  the  condenser  is  fully  charged  the  current 
through  the  arc  rises  to  normal  value,  this  causes  the  volts 
across  the  arc  to  drop.  However,  the  condenser  is  still  fully 


32  RADIO  QUESTIONS  AND  ANSWEES 

charged  and  its  voltage  value  is  now  higher  than  that  of  the 
arc.    It  therefore  discharges  across  the  arc. 

c.  Due  to  the  fact  that  the  discharge  takes  place  through 
a  circuit  having  oscillatory  characteristics,  undamped  etheral 
oscillations  are  produced. 

d.  At  each  oscillation  the  volts  rise  and  fall  periodically, 
giving  a  constant  source  of  energy.    Therefore,  as  long  as  the 
voltage  is  present  the  oscillations  continue. 

Ques.  48.  What  are  the  advantages  of  undamped  waves  ? 

Ans.  Some  of  the  principal  advantages  of  undamped 
waves  are  due  to  the  perfect  syntony  obtainable.  This  per- 
mits close  tuning  and  reduces  interference  between  stations 
which  are  close  together.  The  detector  arrangements  used 
for  the  reception  of  undamped  waves  have  better  mechanical 
features  than  the  crystal  detector  used  for  damp  wave  re- 
ception and  are  not  so  easily  put  out  of  adjustment. 

In  spark  systems  there  are  groups  of  oscillations  separated 
by  comparatively  long  intervals  of  inactivity,  so  that  if  high 
speed  transmission  is  attempted  there  are  not  many  trains  of 
oscillations  per  dot  or  dash,  whereas  with  undamped  oscilla- 
tions these  periods  of  inactivity  are  absent,  hence  high-speed 
work  is  possible  as  soon  as  reception  apparatus  has  been  de- 
veloped which  will  be  automatic  and  efficient. 

Wireless  telephony  has  been  more  successfully  developed 
with  undamped  waves  due  to  the  persistency  of  the  voice- 
carrying  waves. 

With  given  power  much  greater  distances  are  covered  with 
undamped  waves  than  with  damped  waves. 

Another  feature  bearing  on  the  greater  efficiency  of  un- 
damped waves,  is  the  fact  that  longer  waves  can  be  employed 
with  this  type  of  apparatus,  thus  reducing  absorption. 


Part  IV 
STORAGE  BATTERIES 

Ques.  49.    What  is  an  underload  circuit  breaker? 

Ans.  It  consists  of  a  solenoid  switch  which  is  connected 
in  series  to  the  lines  to  be  protected.  Its  position  is  shown 
in  figure  43,  marked  Low  Voltage  Release. 

An  underload  circuit  breaker  is  used  on  storage  battery 
charging  panels  to  open  the  circuit  should  the  voltage  of  the 
generator  fall  below  the  voltage  of  the  battery  being  charged. 
This  prevents  the  battery  from  discharging  back  into  the 
generator,  thus  preventing  possible  damage  of  the  generator 
as  well  as  to  the  battery  itself. 

Edison  Cell 

Ques.  50.  "What  is  the  charging  voltage  of  an  Edison  Cell? 
What  is  voltage  of  charged  cell?  What  is  discharge  voltage 
for  the  normal  functioning  of  cell?  What  is  voltage  of  a 
discharged  cell? 

Ans.  Charging  voltage  is  1.85  volts.  Full  charge  voltage 
is  1.8  volts.  Normal  discharge  voltage  is  1.2  volts. 

Final  useful  cell  voltage  at  normal  rate  is  .9  volts  (Edison 
cells  may  be  discharged  to  any  voltage  down  to  zero,  at  any 
rate,  and  suffer  no  harm,  so  long  as  temperature  does  not 
exceed  115  degrees  Fahr.) 

Ques.  51.  How  is  the  extent  of  charge  of  an  Edison  cell  de- 
termined? Explain  fully. 

Ans.    By  taking  voltage  reading  on  normal  rate  discharge 

and  comparing  it  with  the  normal  charge  voltage  curve.    For 

commercial  practicability  the  ampere  hour  meter  is  used  with 

all  kinds  of  batteries.     It  is  particularly  to  be  remembered 

33 


34  RADIO  QUESTIONS  AND  ANSWERS 

that  the  extent  of  charge  of  an  Edison  cell  cannot  be  deter- 
mined by  taking  a  hydrometer  reading,  as  the  specific  gravity 
of  the  electrolyte  in  this  type  of  cell  does  not  vary  with  charge 
and  discharge. 

Ques.  52.  What  effect  will  charging  an  Edison  cell  have 
on  the  electrolyte? 

Ans.  No  effect,  beyond  losing  some  water  by  electrolysis, 
which  is  replaced  by  flushing  with  distilled  water. 

Ques.  53.  Of  what  material  is  the  positive  and  negative 
plates  of  the  Edison  cell  made? 

Ans.   The  material  in  the  positive  plate  consists  of  alter- 
nate layers  of  nickel  hydroxide  and  exceedingly  thin  flakes 
of  pure  nickel. 

The  negative  plate  material  is  powdered  iron  oxide  with  a 
small  percentage  of  mercury  added  to  increase  conductivity. 

Ques.  54.  Of  what  is  the  electrolyte  of  the  Edison  cell  com- 
posed ? 

Ans.  The  electrolyte  consists  of  a  21  per  cent  solution  of 
Potassium  Hydrate  in  distilled  water  with  a  small  percentage 
of  lithium  hydrate  having  a  specific  gravity  averaging  1.200. 
The  electrolyte  does  not  vary  in  density  during  charge  and 
discharge.  The  Edison  electrolyte  preserves  the  steel  plates. 
Unlike  the  lead-acid  battery,  the  active  materials  are  not 
attacked,  or  eaten  away  by  the  electrolyte. 

Ques.  55.  What  would  be  the  effect  of  charging  an  Edi- 
son cell  in  the  wrong  direction  ?  What  would  be  the  effect  on 
a  lead  cell? 

Ans.  There  would  be  no  damage  done  to  the  Edison  cell 
if  the  temperature  did  not  rise  above  115  degrees  Fahr.  The 
only  effect  would  be  that  the  cell  would  act  as  an  electrolytic 
gas  generator  accumulating  only  a  very  slight  charge  in  the 
reverse  direction. 

If  a  lead  cell  is  charged  in  the  reverse  direction  it  would 
result  in  severe  buckling  of  the  plates,  loosening  of  active 


STORAGE  BATTERIES 


Fig.   22.    Cross   section   Edison    Cell 


material  and  complete  disruption  of  internal  cell  parts.  The 
meters  on  the  board  would  indicate  trouble.  In  all  modern 
battery  equipments  a  circuit  breaker,  or  fuses  in  small  in- 


36  RADIO  QUESTIONS  AND  ANSWERS 

stallations,  is  connected  in  the  circuit  which  protects  against 
such  things  as  charging  in  the  reverse  direction. 

Ques.  56.    Explain  construction  of  an  Edison  cell. 

Ans.  The  following  brief  explanation  of  the  Edison  cell 
may  be  better  understood  by  referring  to  figure  22. 

POSITIVE  PLATE.  The  positive  plate  consists  of 
heavily  nickel  plated  perforated  steel  tubes  arranged  in  rows 
and  filled  with  narrow  layers  of  nickel  hydroxide,  and  ex- 
ceedingly thin  flakes  of  pure  nickel. 

NEGATIVE  PLATE.  The  negative  plate  consists  of  a 
grid  of  nickel  plated  cold  rolled  steel  holding  a  number  of 
rectangular  perforated  pockets  filled  with  powdered  iron 
oxide. 

ASSEMBLY.  The  plates  are  separated  by  narrow  pins  of 
especially  treated  hard  rubber  which  is  riot  injured  by 
electrolyte.  The  end  insulator  is  provided  with  grooves  that 
take  the  edge  of  the  plates,  spacing  and  insulating  them 
from  the  steel  container. 

ELECTROLYTE.  The  composition  of  the  electrolyte 
is  explained  under  question  54. 

Ques.  57.  Can  the  state  of  charge  of  an  Edison  cell  be 
determined  by  means  of  a  hydrometer? 

Ans.   No.     See  question  51. 

Ques.  58.  What  instrument  should  be  used  to  determine 
the  amount  of  charge  of  an  Edison  cell?  Why? 

Ans.  The  Voltmeter.  Because  the  voltage  of  the  Edison 
cell  is  the  only  measurable  difference  between  the  condi- 
tion of  the  cell  when  it  is  fully  charged  and  when  it  is  dis- 
charged. Also  the  ampere  hour  meter  may  be  used.  (See 
question  51).  A  hydrometer  should  never  be  used  because 
the  specific  gravity  of  the  electrolyte  does  not  vary  with 
the  degree  of  charge. 


STORAGE  BATTERIES  37 

Ques.  59.  What  is  the  specific  gravity  of  the  electrolyte 
in  an  Edison  cell?  Does  this  vary  with  charge  and  dis- 
charge ? 

Ans.  The  specific  gravity  of  the  electrolyte  averages  1.200. 
The  specific  gravity  of  the  electrolyte  does  not  vary  appre- 
ciably with  charge  and  discharge;  the  small  loss  is  due  to 
electrolysis. 

Ques.  60.  Is  there  any  action  in  the  electrolyte  of  the 
Edison  cell? 

Ans.  Yes.  As  this  action  is  a  chemical  one  and  would 
require  that  the  reader  have  a  knowledge  of  chemistry,  an 
explanation  is  omitted  from  this  page  and  given  in  the 
appendix  1. 

Ques.  61.  How  do  you  treat  a  storage  cell  that  shows 
signs  of  sulphation? 

Ans.  This  applies  to  lead  cells  only,  the  entire  bank  con- 
taining the  sulphated  cell  should  be  subjected  to  a  long, 
heavy  charge.  If  the  sulphation  is  not  serious  this  treat- 
ment will  restore  the  afflicted  cell  to  normal  condition.  It 
is  best  if  one  or  more  individual  cells  appear  sulphated  while 
the  rest  of  the  battery  is  in  good  condition,  to  remove  such 
cells  and  treat  them  separately  by  giving  them  a  charge  at 
a  high  rate.  If  the  specific  gravity  of  the  electrolyte  of  a 
cell  under  treatment  for  sulphation  rises  above  the  normal 
level,  remove  some  of  the  electrolyte  and  replace  by  pure 
water  until  the  proper  density  is  secured.  Sulphated  plates 
should  be  handled  as  little  as  possible. 

Ques.  62.  At  what  temperature  does  a  storage  battery 
work  best? 

Ans.    Seventy   degrees   Fahrenheit,   air  temperature. 

Ques.  63.  Tell  the  care  necessary  to  place  a  lead  acid 
battery  out  of  service  for  an  indefinite  period. 

Ans.  If  the  battery  is  to  be  put  out  of  service  for  less 
than  a  year  it  should  be  put  into  what  is  called  wet  storage.. 


38  EADIO  QUESTIONS  AND  ANSWERS 

This  is  the  method  usually  applied  to  radio  batteries  pro- 
vided, of  course,  they  do  not  require  repairs  that  will  ne- 
cessitate dismantling.  To  determine  this  a  careful  exam- 
ination of  a  specimen  cell  in  the  battery  is  necessary.  To 
place  a  battery  in  wet  storage  it  is  given  an  equalizing 
charge  and  stored  away  where  it  will  be  free  from  dust. 
The  level  of  the  electrolyte  during  the  period  the  battery 
is  in  storage  must  be  constantly  maintained  about  one-half 
inch  above  the  tops  of  the  plates  by  the  addition  of  distilled 
water.  During  the  storage  period  the  battery  should  be 
given  a  charge  every  four  months  until  the  cells  gas  for  at 
least  three  hours.  Any  cells  not  gasing  should  be  exam- 
ined and  remedied. 

To  place  a  battery  in  dry  storage  it  is  necessary  to  com- 
pletely dismantle  the  various  parts  and  as  this  is  the  work 
of  a  battery  expert  it  should  not  be  attempted  by  the  lay- 
man. 

NOTE:  Those  interested  may  obtain  a  pamphlet  from  the 
Electric  Storage  Battery  Company  of  Philadelphia  giving  full 
directions  for  placing  storage  cells  in  storage. 

Ques.  64.  What  precaution  should  be  taken  in  connection 
with  combining  sulphuric  acid  and  water? 

Ans.  Always  pour  the  acid  slowly  into  the  water.  Never 
pour  the  water  into  the  acid  as  a  violent  chemical  action  takes 
place  which  causes  the  mixture  to  boil  so  violently  as  to  do 
damage. 

Ques.  65.  State  fully  the  care  to  be  given  a  sixty  cell 
Exide  battery  equipment  such  as  is  used  on  shipboard. 

Ans.  A  battery  equipment  regardless  of  type  should  have 
careful  attention.  The  electrolyte  should  be  kept  about  one- 
half  inch  above  the  top  of  the  plates  by  replacing  loss  due 
to  evaporation  with  distilled  water.  The  electrolyte  level 
should  never  be  maintained  by  replacing  acid  unless  the 
electrolyte  is  in  some  way  spilled  out.  The  acid  does  not 


STORAGE  BATTEEIES  39 

evaporate,  it  being  the  water  in  the  electrolyte  that  is  so 
reduced.  It  is  important  that  the  battery  be  kept  fully 
charged,  not  only  so  that  it  may  be  ready  for  immediate  use, 
but  it  is  best  for  the  internal  condition  of  the  individual  cells 
that  they  be  so  kept.  The  condition  of  charge  of  a  lead  cell 
battery  may  be  checked  up  by  taking  combined  hydrometer 
and  voltmeter  readings  of  the  individual  cells.  If  the  cells 
as  a  whole  show  a  comparatively  low  reading  it  shows  that 
they  should  be  charged.  The  low  voltage  reading  indicates 
the  same  condition.  Radio  batteries  should  be  given  a  check 
up  about  once  a  month.  If  a  cell  shows  an  unnatural  condi- 
tion such  as  low  specific  gravity  reading  and  low  voltage 
reading  it  may  indicate  sulphation  or  plate  buckling  and  it 
should  be  cut  out  of  the  circuit  by  disconnecting  the  lead 
strap  connectors  and  jumping  the  bad  cell.  As  soon  as  pos- 
sible the  bad  cell  should  be  taken  out  and  repaired.  The 
battery  should  be  promptly  recharged  when  the  voltage  of 
the  individual  cell  reaches  1.7  volts,  therefore  the  voltage  of 
the  entire  bank  would  read  1.7  X  number  of  cells.  A  battery 
should  not  be  charged  more  frequently  than  once  a  week 
unless  the  service  requires  it.  A  few  simple  rules  listed  below 
apply  to  all  cells. 

a.  Keep  open  flames  away  from  the  battery  at  all  times. 

b.  Eeplace  electrolyte  before  charging. 

c.  When  water  in  cell  evaporates  add  distilled  water. 

d.  Never  allow  cells  to  remain  in   discharged  condition. 

e.  Mix  electrolyte  in  clean  earthen  or  glass  jars. 

f.  AlloAV  solution  to  cool  before  putting  into  cell. 

g.  Never   pour   water   into   sulphuric   acid, 
h.  Never  allow  salt  to  get  into  cell. 

i.    Use  only  absolutely  pure  chemicals  and  water. 

j.  Always  provide  plenty  of  ventilation. 

k.  If  burned  by  sulphuric  acid  apply  ammonium  hydroxide  or  soda. 


40  RADIO  QUESTIONS  AND  ANSWERS 

Over  sulphation  may  be  caused  by : 

1.  Wrong  specific  gravity  of   electrolyte. 

2.  Overdischarge. 

3.  Allowing  cell  to  remain  too  long  in  a  discharged  con- 
dition. 

Ques.  66.  What  determines  the  capacity  of  a  storage  cell? 
What  is  the  unit  of  capacity  of  a  cell! 

Ans.  The  capacity  of  a  storage  cell  is  determined  by  the 
number  of  plates  and  by  the  amount  of  available  active  ma- 
terial contained  in  the  individual  cells. 

The  unit  of  capacity  is  the  ampere  hour.  A  battery  is 
rated  as  having  so  many  ampere  hours  capacity. 


Part  V 
MOTORS  AND  GENERATORS 

Ques.  67.  Describe  a  compound  wound  motor.  "Where  is 
the  rheostat  controlling  the  speed  regulation  connected  in  a 
compound  motor? 

Ans.  A  compound  motor  has  both  series  and  shunt  field 
coils.  The  shunt  field  is  wound  with  small  wire  and  the  series 
field  is  wound  with  heavy  wire.  The  series  field  is  in  series  with 
the  armature  and  the  shunt  field  is  connected  in  shunt  or  par- 
allel to  the  armature.  A  wiring  diagram  of  a  compound  motor 
is  shown  in  figure  23.  A  cut  of  a  compound  motor  field  coil  is 


field  Rheostat- 
Fig.  23.  Wiring  Diagram   Compound  Motor 

shown  in  figure  24.  Note  the  heavy  series  winding  on  the 
end  of  the  core.  The  shunt  winding  takes  up  most  of  the 
winding  space.  The  rheostat  controlling  the  speed  is  con- 
nected in  the  shunt  field  as  shown  by  the  diagram. 

Ques  68.  What  will  cause  a  motor  and  also  a  generator  to 
overheat  ? 

Ans.  Overheating  of  motors  and  generators  is  usually 
caused  by  either  lack  of  oil  on  the  bearings  or  overloading 
the  machine.  Grooved  bearings  or  a  sprung  shaft  may  cause 
heating. 

41 


42  RADIO  QUESTIONS  AND  ANSWERS 

Ques.  69.  If  a  generator  field  burned  out  what  would  be 
the  effect? 

Ans.    No  E.  M.  F.  would  be  generated. 

Ques.  70.  What  is  the  difference  between  a  motor  and  a 
generator  ? 

Ans.  A  motor  is  a  machine  for  transforming  electrical 
energy  into  mechanical  energy.  A  generator  (A.C.  or 
D.C.)  changes  mechanical  energy  into  electrical  energy. 


Fig.    24.   Field    Coil   Compound   Motor 

Ques.  71.  What  is  the  difference  between  an  A.C.  generator 
and  a  D.C.  motor? 

Ans.  Aside  from  the  difference  noted  in  the  question  above 
an  A.C.  generator  may  have  slip  rings  and  a  D.C.  motor 
always  has  a  commutator.  There  is  also,  of  course,  a  dif- 
ference in  the  electrical  design. 

Ques.  72.  How  are  the  fields  of  a  generator  generally  ex- 
cited ? 


MOTORS  AND  GENERATORS  43 

Ans.  In  radio  practice  the  field  of  the  generator  or  alter- 
nator is  usually  separately  excited  as  shown  in  figure  25, 
by  connecting  the  field  directly  in  parallel  to  an  external 
source  of  direct  E.M.F. 

Ques.  73.    How  is  the  voltage  of  a  generator  increased  ? 

Ans.  The  voltage  of  a  generator  may  be  increased  by  in- 
creasing the  field  excitation.  This  may  be  done  by  decreasing 
the  resistance  of  a  field  rheostat  which  controls  the  current 
flowing  into  the  generator  field. 


Fig.  25.  Separately  excited  generator  field 

Ques.  74.    Explain  fully,  no  load  and  full  load  voltage. 

Ans.  No  Load  Voltage  is  the  pressure  generated  when 
the  machine  has  no  external  load.  In  radio  transmitters,  this 
is  the  condition  when  the  key  is  not  closed.  This  value  is 
the  one  given  as  the  rated  voltage  of  the  machine,  for  example : 
a  110  volt  generator  gives  110  volts  on  no  load. 

Full  Load  Voltage  is  the  resultant  pressure  when  the 
machine  is  connected  to  an  external  load.  When  a  load  is 
placed  on  the  machine  the  voltage  drops  to  a  lower  figure, 
depending  upon  the  load  value.  This  is  illustrated  when  the 
key  to  a  transmitting  set  is  closed  and  the  voltage  of  the  gen- 
erator immediately  drops  to  a  lower  value  depending  upon 
the  power  being  used. 

Ques.  75.  An  alternator  has  24  poles  and  a  speed  of  3600 
R.P.M.  What  is  the  frequency? 

Ans.  The  frequency  of  the  generator  may  be  found  by 
multiplying  the  number  of  pairs  of  poles  by  the  revolutions 
per  second.  In  this  case,  if  there  are  24  poles,  there  are  12 


44  RADIO  QUESTIONS  AND  ANSWERS 

pairs  of  poles.  If  the  speed  is  3600  R.P.M.,  the  speed  per 
second  would  be  1/60  of  that  or  60  R.P.  Second.  Therefore 
the  frequency  is  Pairs  of  Poles  12  X  60  —  720  or  Answer: 
720  cycles. 

Ques.  76.  Give  the  function  of  the  commutator  of  the  D.C. 
motor. 

Ans.  The  function  of  the  commutator  of  the  D.C.  motor 
is  to  maintain  proper  direction  of  armature  current  under 
each  field  pole.  As  the  various  armature  conductors  pass 
from  one  pole  to  the  next,  the  direction  of  current  flow  is 
thus  automatically  changed,  resulting  in  a  constant  turning 
effort  (torque)  in  one  direction. 

On  a  generator  the  commutator  commutes  or  rectifies  the 
induced  E.M.F.  in  the  armature  conductors  and  conveys  the 
E.M.F.  to  outside  conductors  in  one  direction  only. 

Ques.  77.  What  is  the  effect  of  starting  a  motor  too  sud- 
denly or  too  slowly? 

Ans.  Starting  a  motor  too  quickly  will  cause  the  breakers 
to  trip  or  the  fuses  to  blow.  This  is  due  to  the  low  resistance 
of  the  armature  circuit  and  lack  of  counter  E.M.F.  before 
it  comes  up  to  speed.  If  there  were  no  fuses  or  breakers  in 
the  line  the  armature  winding  would  burn  out. 

Starting  a  motor  too  slowly  may  burn  out  the  resistance 
units  in  the  starting  box  as  they  are  made  for  temporary  duty 
only  and  cannot  stand  a  heavy  current  flow  for  more  than  a 
very  short  period. 

Ques.  78.    Why  are  collector  rings  used  on  an  alternator? 

Ans.  The  function  of  the  collector  rings  is  to  conduct  the 
alternating  E.M.F.  induced  in  the  armature  coils  to  outside 
conductors. 

Ques.  79.    What  is  a  water  rheostat? 

Ans.  A  water  rheostat  consists  of  a  container,  made  of 
insulating  material  such  as  wood  or  fibre,  filled  with  salt 
water  into  which  are  placed  three  plates.  This  arrangement 


MOTORS  AND   GENEEATOE8 


4.1 


is  placed  in  the  circuit  as  shown  in  figure  26,  and  the  resistance 
varied  by  making  the  distance  between  the  plates  greater  or 
smaller,  respectively,  for  high  or  low  resistance.  As  an  ex- 
ample, if  such  a  rheostat  is  used  in  place  of  the  starting  box 
in  a  shunt  motor  circuit,  the  plates  are  first  put  in  such  a 
position  that  the  plate  A  is  nearest  plate  B.  In  this  position 
the  resistance  in  the  field  circuit  is  at  a  minimum  and  allows 


To  start  motor  move  plate  A 
in  direction  of  arrow 

Fig.  26.  Water  Rheostat 

a  strong  current  to  flow  in  the  field  while  the  conditions  in 
the  armature  circuit  are  the  reverse. 

Plate  A  is  at  a  maximum  distance  from  plate  C  and  a 
maximum  resistance  value  is  in  the  armature  circuit  allowing 
only  a  small  current  to  flow  which  is  desirable  when  starting 
a  motor.  The  movable  plate  A  is  then  moved  in  the  direc- 
tion of  the  arrow  toward  C  and  the  resistance  in  the  field 
circuit  is  increased,  decreasing  the  field  current,  while  the 
resistance  in  the  armature  circuit  is  decreased,  increasing  the 
armature  current  as  the  plate  A  approaches  plate  C  and  as 
the  motor  gains  speed. 

A  water  rheostat  may  be  used  in  an  emergency  when  other 
rheostats  are  burned  out  or  out  of  order.  This  type  of 
rheostat  is  also  used  in  electrical  laboratories. 

Qucs.  80.  What  is  the  no-field-voltage  release  magnet,  and 
where  is  it  placed? 


46  RADIO  QUESTIONS  AND  ANSWERS 

Am.  The  no-voltage  release  is  incorporated  as  part  of  the 
starting  box.  It  is  a  small  electromagnet  and  is  placed  in 
such  a  position  that  when  the  handle  of  the  starter  is  in  full 
running  position  it  is  held  in  that  position  by  the  magnetic 
attraction  of  the  no-voltage  release.  The  winding  of  the  no- 
voltage  release  is  placed  in  series  with  the  field  winding  of 
the  motor.  If  the  field  winding  circuit  is  opened  in  any  way 
the  starting  box  handle  springs  back  to  starting  position. 
This  action  safeguards  the  machine  from  being  burned  out; 
for  if  the  starting  handle  remained  in  full-speed  position  and 
the  current  were  suddenly  turned  on  when  the  motor  was 
stopped,  the  sudden  inrush  of  current  to  the  motor  armature 
would  burn  it  out  because  there  would  be  no  counter  E.M.F. 
generated  to  buck  the  incoming  current  and  to  hold  it  to 
safe  limits.  The  no-voltage  release  is  shown  in  figure  23. 


Part  VI 
RECEIVING  APPARATUS 

Ques.  81.  What  means  are  provided  in  a  receiving  system 
to  protect  it  from  injury  by  signals  transmitted  on  high  power 
in  the  nearby  vicinity? 

Ans.  A  safety  gap  of  very  short  length  is  connected  be- 
tween the  antenna  and  the  ground  on  receiving  equipment 
at  the  point  where  the  antenna  lead  and  the  ground  lead  make 
connection  to  the  apparatus.  Strong  signals  will  discharge 
across  the  gap  and  form  a  short  path  to  the  ground  and  in 
that  way  they  are  prevented  from  passing  through  the  re- 
ceiving apparatus  and  can  do  no  damage  to  it.  Some  types 
of  receivers  are  fitted  with  a  very  high  resistance  conductor 
which  is  connected  directly  across  the  antenna  and  ground. 
Such  a  protective  device  allows  currents  of  such  value  as  to 
be  of  a  damaging  nature  to  pass  directly  to  the  earth.  It 
is  of  course  possible  in  inductively  coupled  types  of  apparatus 
to  quickly  decrease  the  coupling  and  in  that  way  the  mutual 
induction  between  the  circuits  is  decreased  so  that  the  high 
potential  current  does  not  flow  through  the  secondary  circuit 
where  it  might  do  damage. 

Ques.  82.  Describe  a  receiving  system  employing  hetrodyne 
principles. 

Ans.  There  are  two  kinds  of  hetrodyne  receivers,  viz. :  Ex- 
ternal hetrodyne  and  self -hetrodyne.  The  former  is  not  used 
to  any  extent  at  the  present  time  having  been  superseded 
largely  by  the  latter.  One  type  of  self -hetrodyne  is  shown 
in  figure  27.  Coil  L2  is  coupled  to  a  primary  coil  in  the 
antenna  circuit. 

47 


EADIO  QUESTIONS  AND  ANSWERS 


The  important  feature  of  this  hookup  is  that  the  plate  is 
coupled  to  the  grid  circuit  through  the  inductance  L^  reacting 
on  L2. 

Ques.  83.  Draw  a  diagram  of  a  receiving  system  employing 
audion  tubes;  (a)  As  a  detector,  (b)  With  one  step  of  am- 
plification, (c)  With  two  steps  of  amplification. 


Fig.  27.  Self  Hetrodyne 

Ans.  See  figures  28,  29  and  30  below.  The  inductance, 
figure  28,  is  coupled  to  a  primary  coil  in  the  antenna  circuit 
when  receiving  distant  signals. 

Ques.  84.  How  would  you  adjust  a  receiving  system  em- 
ploying an  audion  detector  to  the  given  wavelength  of  a 
transmitter  ? 


Fig.  28.  Audion  Detector 

Ans.  To  adjust  an  audion  detector  receiver  to  a  given 
wavelength,  light  the  filament  by  closing  the  filament  circuit 
switch.  Care  must  be  taken  not  to  burn  the  filament  too 
brightly  as  the  strength  of  the  signals  do  not  always  increase 


RECEIVING  APPARATUS 


49 


Fig.  29.   One  Step  Amplifier 

with  filament  current.  Next  close  the  B  battery  switch  and 
adjust  the  secondary  and  primary  circuits  to  the  desired 
wavelength.  If  no  signals  are  heard  it  may  be  that  the 
polarity  of  either  the  filament  cr  plate  battery  is  reversed, 
the  remedy  in  this  case  is  to  change  the  connections, 


Fig.  30.   Two  Step  Amplifier 


50  RADIO  QUESTIONS  AND  ANSWERS 

Ques.  85.    Draw  a  diagram  of  a  standard  receiving  circuit 
employing  a  crystal  detector  and  potentiometer. 
Ans.    See  figure  31  below. 


Fig.    31.    Beceiver,   crystal   detector 

86.    Describe  a  variometer  to  be  used  in  connection 
with  a  receiving  system. 

Ans.  The  variometer  consists  of  two  hoop  form  coils  of 
wire  wound  on  forms.  One  of  the  coils  is  stationary  and  the 
other  moves  inside  the  stationary  coil.  The  two  coils  are  con- 


Fig.   32.  Variometer 

(Courtesy,  General  Radio  Co.) 


RECEIVING  APPARATUS  51 

nected  in  series.  Figure  32  shows  a  form  of  variometer. 
The  movable  coil  has  a  scale  attached  on  the  top  of  the  cabinet 
which  shows  the  relative  positions  of  the  coils.  When  the 
coils  are  in  a  position  so  that  their  magnetic  fields  buck  one 
another  the  inductance  is  at  a  minimum.  The  advantage  of 
the  variometer  is  that  there  are  no  movable  switches  to  be 
adjusted  when  tuning.  A  very  fine  variation  of  wavelength 
is  possible. 

Ques.  87.  Show  by  diagram  two  means  of  connecting  a 
test  buzzer  to  a  crystal  detector.  Explain  their  advantage 
and  connection  fully. 

Ans.     See  figure  33  below. 


Fig.  33.     Buzzer  Detector  Tester 

A  test  buzzer  connected  as  in  figure  33,  if  connected  induc- 
tively or  directly  is  of  advantage  in  testing  whether  or  not 
the  receiving  apparatus  as  a  whole  is  in  working  condition. 
This  function  can  be  performed  by  a  test  buzzer  because  it 
generates  electromagnetic  waves  which  have  an  effect  upon 
the  receiving  cricuit  similar  to  the  electromagnetic  waves  re- 
ceived from  a  distant  transmitter.  A  test  buzzer  is  of  very 


52  BADIO  QUESTIONS  AND  ANSWERS 

great  value  when  a  crystal  detector  is  used  as  it  is  the  only 
absolute  method  of  making  sure  that  the  detector  point  is  on  a 
sensitive  spot  on  the  crystal. 

Ques.  88.  What  is  the  meaning  of  the  term  "stand  by" 
circuit  in  connection  with  a  receiving  system. 

Ans.  A  "stand  by"  circuit  is  one  that  is  tuned  broadly. 
With  a  circuit  of  this  kind  a  wide  range  of  wavelengths  can 
be  heard  and  for  this  reason  it  is  valuable  for  general  listen- 
ing in. 

Ques.  89.  Why  is  it  necessary  to  employ  a  diaphram  in 
connection  with  head  receivers? 

Ans.  It  is  the  vibration  of  the  diaphram  that  produces  the 
sound  in  the  head  receiver.  The  diaphram  is  acted  upon  by 
the  magnets  in  the  receiver  and  vibrates  at  a  certain  speed 
depending  upon  the  frequency  of  magnetic  attraction  exerted 
by  the  magnets.  High  frequency  of  vibration  gives  a  high 
tone  and  likewise  low  frequency  gives  low  tone.  In  spark 
transmitters  the  received  tone  is  directly  dependent  upon  the 
spark  frequency.  In  undamped  systems  the  tone  may  be 
varied  at  the  will  of  the  operator. 

Ques.  90.  Describe  the  electrical  and  magnetic  phenomena 
in  connection  with  the  proper  functioning  of  the  head  re- 
ceiver. 

Ans.  In  order  to  clearly  understand  the  working  of  a 
telephone  receiver  it  is  necessaiy  to  know  the  principal  parts 
of  which  it  is  composed.  Figure  34  shows  a  side  cut  of  a 
watch  case  type  such  as  is  used  in  radio  work. 

Note  that  the  diaphram  is  placed  so  that  it  will  be  affected 
by  the  magnets.  The  magnets  are  permanent  electromagnets 
and  the  magnetism  in  them  has  a  holding  effect  on  the 
diaphram.  However,  a  more  pronounced  movement  of  the 
diaphram  towards  and  away  from  the  pole  pieces  takes  place 
when  a  pulsating  E.M.F.  is  applied  to  the  coils.  When  no 


RECEIVING  APPARATUS 


53 


current  is  flowing  in  the  magnet  coils  the  position  of  the 
diaphram  is  as  in  position  A,  which  is  normal. 


Fig.  34.  Telephone  Keceiver 

When  the  current  flows  through  coils  a  magnetic  field  is 
set  up  which  draws  the  diaphram  towards  the  pole  faces  posi- 
tion B.  When  the  current  stops  the  diaphram  returns  to 
normal  position,  but  may  spring  back  to  position  C.  It  is 
seen  that  every  time  the  diaphram  moves  from  normal  position 
to  the  position  nearest  the  pole  faces  and  back  to  normal  a 
click  is  produced.  If  these  clicks  are  made  to  occur  in  rapid 
succession  a  continuous  sound  is  produced.  A  study  of  the 
graphs,  figure  35,  will  show  the  relation  of  the  ether  oscilla- 
tions to  the  final  telephone  current. 

Wave  Trains 


AA 


A 


Effect  of  Rectifier 


Current-  m  Telephone's 

Fig.    35.    Wavetraiii    to    Telephone    Current    Curve 

If  the  spark  frequency  is  steady  and  the  sparks  discharge 
across  the  gap  at  regular  intervals  the  note  in  the  headphone 
will  be  smooth.  If,  on  the  other  hand,  the  intervals  between 
the  sparks  are  uneven,  an  uneven  note  will  be  heard  in  the 
head  receiver. 

Ques.  91.  Describe  magnetic  coupling.  Describe  electro- 
static coupling. 


54 


RADIO  QUESTIONS  AND  ANSWERS 


Ans.  Magnetic  Coupling  is  any  coupling  which  takes  place 
by  means  of  magnetic  lines  of  force.  The  autotransformer 
is  used  to  give  direct  magnetic  coupling  and  the  oscillation 
transformer  gives  inductive  magnetic  coupling.  Both  are 
types  of  magnetic  coupling.  See  figures  36a  and  b.  The  term 


Fig.  36.  Magnetic  and  Static  Coupling 

electromagnetic  coupling  is  used  synonymously  with  magnetic 
coupling.  Electrostatic  coupling  takes  place  through  a  con- 
denser as  shown  in  figure  36c. 

Ques.  92.  Describe  what  happens  to  a  wave  train  when 
it  strikes  the  receiving  aerial. 

Ans.  "When  an  advancing  wave  train  strikes  an  aerial  it 
cuts  the  wires  of  which  the  aerial  is  composed  and  induces 
an  E.M.F.  therein.  This  E.M.F.  causes  oscillations  in  the 
aerial  circuit  as  long  as  the  cutting  continues.  There  is  con- 
nected in  the  aerial  circuit  directly  or  by  means  of  inductive 
coupling  a  detector  or  rectifying  instrument  which  breaks 
up  the  antenna  oscillations  into  a  series  of  low  frequency 
unidirectional  pulses  which  are  audible  in  the  telephone  re- 
ceiver. 

Ques.  93.  How  do  you  proceed  to  calibrate  a  receiving  set 
with  a  wavemeter? 

Ans.  To  calibrate  a  receiving  set  the  wavemeter  must  act 
as  a  transmitter.  This  is  accomplished  by  means  of  a  buzzer 


RECEIVING  APPARATUS 


55 


as  shown  in  figure  37.  First  start  the  buzzer  and  tune  the 
wavemeter  to  the  lowest  wavelength  to  which  the  receiving 
set  is  to  be  tuned.  Tune  the  primary  circuit  of  the  receiver 
to  resonance  with  the  wavemeter  by  varying  any  movable 
inductance  or  capacity  handles  in  the  circuit  and  note  the 
final  positions  on  a  sheet.  The  secondary  or  closed  circuit 
may  then  be  adjusted  until  the  loudest  signal  is  heard.  This 
is  done  by  moving  inductance  switches  and  condenser  handles. 
The  final  positions  of  each  can  be  noted  on  a  sheet.  The 


Fig.  37.     Tuning  Eeceiver  with  a  Wavemeter 

wavemeter  may  now  be  tuned  to  the  next  higher  wavelength 
and  a  similar  operation  gone  through.  These  operations  to 
be  repeated  for  each  successive  wavelength. 

The  wavemeter  must  be  placed  in  close  proximity  to  the 
receiver  and  coupled  to  it  as  shown  in  the  diagram.  A  sample 
tuning  sheet  is  shown  in  figure  38. 

Ques.  94.  Describe  and  explain  the  operation  of  a  Poulsen 
ticker. 

Ans.  A  Poulsen  Ticker  consists  of  a  segmented  wheel  with 
certain  segments  electrically  connected  together  so  that  a 
conducting  path  is  connected  between  stationary  brushes  at 
predetermined  intervals.  This  wheel  is  mounted  on  a  motor 
shaft  and  connected  in  place  of  the  detector  in  the  receiver 
circuit  and  serves  to  break  up  undamped  oscillations  into  low 
frequency  groups  so  they  may  be  audible  in  the  headphones. 


RADIO  QUESTIONS  AND  ANSWERS 


Ques.  95.  Describe  the  operation  of  the  slipping  contact 
detector. 

Ans.  A  Slipping  Contact  Detector  consists  of  a  grooved 
brass  wheel  mounted  on  a  motor  shaft.  A  wire  brush  is  so 
arranged  as  to  make  slipping  contact  when  the  wheel  rotates. 
The  wheel  and  brush  connections  are  connected  in  place  of  the 


Wave 
Length 

Primary 

Primary 
ConcT 

Secon- 
dary 

Secondary 

Coupling 

200 

250 

300 

350 

400 

450 

500 

550 

600 

650 

TOO 

750 

800 

850 

900 

950 

1000 

Fig.  38.  Tuning  Sheet 

crystal  detector.  The  theory  of  operation  is  that  the  slipping 
contact  is  one  of  variable  resistance  and  therefore  causes 
variable  charges  to  accumulate  in  the  telephone  condenser. 
The  note  in  the  headtelephones  will  vary  in  accordance  with 
the  speed  at  which  the  wheel  rotates. 

Ques.  96.  Why  is  it  necessary  to  employ  detecting  elements 
to  render  radio  signals  audible? 

Ans.  Electrical  ether  waves  have  a  frequency  from  20,000 
cycles  up.  Frequencies  above  this  limit  are  ordinarily  in- 
audible. If  the  headtelephones  were  energized  by  the  fre- 
quency direct  and  the  diaphram  vibrated  at  this  frequency, 
nothing  would  be  heard  as  it  is  above  audibility.  It  is  there- 
fore necessary  to  rectify  these  high  frequency  oscillations  into 


RECEIVING  APPARATUS  57 

a  pulsating  E.M.F.  which  can  be  heard  in  the  headphones. 
This  rectification  is  shown  graphically  in  figure  35. 

Ques.  97.  Why  are  permanent  magnets  used  in  headtele- 
phones  ? 

Ans.  Permanent  magnets  produce  a  greater  response  for  a 
given  current  than  is  obtained  with  soft  iron  magnets. 

Ques.  98.  How  would  you  test  for  a  short  circuit  in  an  air 
dielectric  condenser? 

Ans.  A  low  potential  condenser  with  air  dielectric  may 
be  tested  for  a  short  circuit  in  several  ways.  One  of  the 
simplest  would  be  to  connect  the  condenser  under  test  in 
parallel  to  the  headtelephones,  leaving  one  side  of  the  circuit 
loose  so  that  it  can  be  connected  and  disconnected  quickly. 
When  radio  signals  are  heard  if  the  parallel  condenser  cir- 
cuit is  completed  and  the  condenser  is  not  short  circuited, 
signals  will  be  heard  as  before.  This  test  can  only  be  used 
where  it  is  possible  to  receive  loud  signals  as  the  capacity 
of  the  condenser  across  the  headtelephones  may  render 
weak  signals  inaudible.  Another  and  more  simple  test  would 
be  to  insert  a  headphone  and  dry  cell  in  series  with  the 
condenser  and  if  short-circuited,  a  click  would  be  heard  in 
telephones. 

Ques.  99.  Explain  how  you  would  tune  in  signals  with  an 
inductively  coupled  receiver. 

Ans.  A  simple  inductively  coupled  receiver  is  shown  in 
figure  39.  To  receive  signals  make  sure  the  antenna  and 
ground  connections  are  made.  Set  the  crystal  detector  D 
to  a  sensitive  position  as  determined  with  the  aid  of  a  test 
buzzer.  Set  the  variable  condenser  V.C.  near  the  minimum 
value  and  closely  couple  the  secondary  S  to  the  Primary  P. 
Listen  carefully  and  vary  the  contact  1  until  the  maximum 
signal  is  heard.  Next  vary  the  inductance  value  of  the  sec- 


(58  RADIO  QUESTIONS  AND  ANSWERS 

ondary  by  moving  the  contact  2  until  the  signal  strength  is 
increased  to  a  new  maximum.  The  variable  secondary  con- 
denser V.C.  may  now  be  varied  for  maximum  signal  strength. 
If  interference  from  other  stations  is  heard,  the  coupling 
should  be  decreased  by  moving  the  secondary  away  from  the 
primary.  It  is  well  to  remember  that  generally  louder  signals 
are  obtained  with  a  maximum  value  of  secondary  inductance 
and  a  minimum  value  of  secondary  capacity.  To  avoid  inter- 


Fig.  39.  Inductively  Coupled  Receiver 

ference  from  other  stations,  work  with  the  smallest  degree  of 
coupling  possible. 

Ques.  100.  Why  are  low  resistance  phones  not  used  with 
any  type  of  modern  detector? 

Ans.  The  current  flowing  in  the  telephone  circuit  of  a 
radio  receiving  set  is  of  very  small  value.  In  order  that  a 
strong  electromagnetic  field  may  be  generated  by  this  feeble 
current,  a  great  number  of  turns  of  wire  must  be  included. 
To  illustrate,  let  us  assume  that  a  force  strong  enough  to 
lift  100  Ibs.  must  be  produced  by  a  given  magnet.  If  one  turn 
produces  a  force  strong  enough  to  lift  one  pound,  more  turns 
would  be  necessary  for  the  magnet  desired.  Therefore  adding 
ampere  turns  increases  the  magnetic  power  of  a  magnet. 

To  apply  the  above  example  to  radio  receivers  it  is  readily 
seen  that  in  order  for  the  very  feeble  currents  flowing  in  tho 


RECEIVING  APPARATUS  59 

telephones  circuit  to  produce  a  strong  field,  a  great  many 
turns  of  wire  must  be  wound  on  the  magnet.  All  wire  has 
resistance,  therefore,  relatively  speaking,  a  telephone  with  a 
great  number  of  turns  such  as  is  needed  in  radio  will  have  a 
high  resistance.  Low  resistance  telephones  have  less  turns 
and  therefore  less  ampere  turns  than  high  resistance  phones, 
therefore,  the  latter  are  desirable  for  use  with  radio  detectors. 
Commercial  receivers  of  today  are  wound  between  2000  and 
3000  ohms. 

Ques.  101.  What  is  the  function  of  a  fixed  condenser  in 
a  receiving  circuit? 

Ans.  The  fixed  condenser  is  usually  connected  in  parallel 
to  the  telephones.  In  this  position  it  provides  a  complete 
circuit  for  the  oscillations  in  the  secondary  circuit  without 
having  to  flow  through  the  telephones,  the  high  induction 
of  which  would  tend  to  choke  back  the  oscillations  and  possibly 
prevent  their  detection. 

Ques.  102.  Explain  how  a  buzzer  tester  may  be  used  to 
locate  faults  in  a  receiving  circuit. 

Ans.  If  a  certain  part  of  the  receiving  apparatus  is  sus- 
pected of  being  open  circuited  or  short  circuited,  a  buzzer 
tester  may  be  used  to  locate  the  trouble.  To  test  for  an  open 
or  short  circuit  connect  the  buzzer  in  series  with  the  circuit 
under  test.  If  the  buzzer  operates,  the  current  path  is  com- 
plete, if  it  does  not,  the  current  path  is  open.  An  open 
circuit  is  indicated  by  lack  of  operation  of  the  buzzer.  A 
closed  circuit  is  indicated  by  operation  of  the  buzzer.  The 
test  may  be  applied  to  each  piece  of  apparatus  separately  until 
the  trouble  or  series  of  troubles  is  located. 

Ques.  103.  How  should  the  receiving  set  be  adjusted  to  a 
certain  transmitting  station  during  heavy  static? 

Ans.  To  receive  in  heavy  static,  extremely  loose  coupling 
is  required.  It  is  necessary  when  using  loose  coupling  to 
tune  very  carefully,  as  a  small  variation  from  the  proper  posi- 


60  RADIO  QUESTIONS  AND  ANSWERS 

tion  will  tune  most  signals  out.  When  using  loose  coupling 
on  an  inductively  coupled  set,  it  is  necessary  to  increase 
secondary  capacitance  as  the  coupling  is  increased  and  to 
decrease  slightly  the  secondary  inductance. 

Ques.  104.  What  is  the  advantage  of  a  variable  condenser 
across  the  secondary  of  a  receiving  transformer  ? 

Ans.  The  secondary  variable  condenser  permits  accurate 
tuning  of  the  secondary  circuit  to  the  antenna  circuit. 

Ques.  105.  Explain  two  methods  of  receiving  undamped 
signals. 

Ans.     (a)  Heterodyne,  (b)  Ticker. 

The  heterodyne  method  is  one  in  which  a  local  current  of 
radio  frequency  is  superimposed  upon  an  incoming  frequency 
of  electromagnetic  waves,  resulting  in  a  frequency  equal  to 
the  difference  between  the  incoming  and  the  superimposed 
frequencies.  For  example,  if  the  incoming  radio  frequency 
is  100,000  cycles  per  second,  the  local  frequency  99,000  cycles, 
then  the  resultant  note  will  have  a  frequency  of  1000  pulses 
per  second. 

The  ticker  method  of  undamped  wave  reception  is  explained 
under  question  No.  94. 

Ques.  106.    Give  a  diagram  of  an  audibility  meter. 

Ans.  A  diagram  of  an  audibility  meter  manufactured  by 
the  General  Radio  Company  is  given  below,  figure  40. 


Audibility  Meter 

Fig.    40.    Audibility   Meter 


Part  VII 
VACUUM   TUBES 

Ques.  107.  What  is  the  usual  plate  voltage  employed  to 
function  an  audion  detector? 

Ans.  The  usual  plate  voltage  is  22.5  volts  and  is  usually 
supplied  by  a  standard  22y2  volt  dry  battery  or  a  storage 
battery. 

Ques.  108.  What  means  are  usually  provided  for  supply- 
ing filament  current  for  the  successful  operation  of  a  vacuum 
tube  detector? 

Ans.  The  filament  current  is  supplied  by  storage  batteries 
in  most  cases. 

Ques.  109.  What  is  the  difference  between  a  Fleming  valve 
and  an  audion  detector? 

Ans.  The  Fleming  valve  has  two  elements,  a  plate  and  a 
filament.  The  audion  has  three  elements,  a  plate,  a  grid,  and 
a  filament. 

Ques.  110.    How  may  the  sensitivity  of  a  valve  be  increased  ? 

Ans.    The  sensitivity  of  a  vacuum  tube  depends  upon : 

a.  Correct  filament  brilliancy. 

b.  Correct  plate  voltage. 

c.  Degree  of  vacuum. 

The  filament  current  may  be  adjusted  by  the  A  battery 
rheostat  while  signals  are  received  and  left  in  the  position  of 
maximum  signal.  It  frequently  happens  that  the  B  battery 
supplying  the  plate  voltage  drops  in  voltage  very  quickly 
after  reaching  a  certain  point  of  discharge.  Therefore,  care- 
ful attention  must  be  paid  to  the  state  of  charge  of  this 
61 


62  EADIO  QUESTIONS  AND  ANSWERS 

battery.  After  the  vacuum  tube  set  has  been  operated  for 
some  little  time,  charging  the  B  battery  invariably  increases 
its  sensitiveness.  The  degree  of  vacuum  has  a  marked  effect 
upon  the  sensitivity  of  a  vacuum  tube.  If  after  long  use  it  is 
suspected  that  the  degree  of  vacuum  is  becoming  less,  the  tube 
may  be  held  over  a  candle  flame  until  the  bulb  becomes  warm. 
This  will  in  some  cases  partly  restore  the  vacuum  and  inci- 
dently  increase  the  sensitivity  of  the  bulb. 

Ques.  111.  Describe  an  audion  detector.  What  is  its  basic 
principle? 

Ans.  An  audion  detector  consists  of  an  exhausted  glass 
bulb  containing  three  elements,  filament,  plate  and  grid.  The 
basic  principle  of  its  operation  is  that  when  a  metal  is  heated 
above  red  heat  a  violent  electronic  emission  occurs.  In  the 
audion  these  electrons  are  given  off  by  the  filament  and  strike 
the  plate.  The  intensity  of  electron  flow  from  filament  to 
plate  is  controlled  by  the  grid.  The  stream  of  electrons  ex- 
plained above  will  act  as  a  conducting  path  for  an  electric 
current  more  favorably  in  one  direction  under  certain  adjust- 
ments. Therefore,  it  can  be  used  as  a  rectifier  and  this  is 
its  function  when  used  as  a  detector. 

. .  Ques.  112.  What  instrument  is  used  to  regulate  the  current 
to  the  filament  and  what  is  the  purpose  for  such  regulation? 

Ans.  The  filament  current  in  a  vacuum  tube  is  regulated 
by  a  low  resistance  rheostat.  The  reason  for  such  regulation 
is  that  the  sensitiveness  of  the  tube  is  increased  by  careful 
regulation  of  the  filament  current.  The  filament  current 
rheostat  also  prevents  a  recuperated  battery  from  burning  out 
the  filament  when  it  is  first  lighted. 

Ques.  113.  What  is  the  effect  of  reversed  polarity  on  the 
plate  and  filament  circuit  of  a  vacuum  tube? 

Ans.  If  the  plate  connections  are  of  reversed  polarity  no 
signals  will  be  heard.  If  the  filament  circuit  is  reversed 
signals  may  be  heard  although  of  decreased  intensity. 


Part  VIII 
LAWS   AND   TRAFFIC   REGULATIONS 

Ques.  114.  What  is  the  U.  S.  distance  requirement  for 
auxiliary  equipment? 

Ans.  The  auxiliary  equipment  must  be  able  to  send  one 
hundred  miles  for  a  period  of  four  hours  at  the  least. 

Ques.  115.  Give  the  complete  procedure  in  calling  a  sta- 
tion. 

Ans.  Before  calling  a  station  the  operator  must  first  make 
sure  that  the  station  he  wishes  to  call  is  not  busy;  secondly, 
that  he  will  interfere  with  no  authorized  traffic  already  going 
on.  If  the  transmission  may  be  made  proceed  as  follows : 

Example : 

Ship  KQP  calls  NAH 

NAH  NAH  '  NAH 

KQP  KQP  KQP 

Ques.  116.    Give  the  complete  procedure  in  answering  a  call. 
Ans.     Example: 

NAH  having  been  called  answers 

KQP     KQP     KQP 

NAH 

Ques.  117.  Has  the  master  of  the  vessel  the  right  to  censor 
all  messages  received  and  transmitted  by  the  radio  station? 

Ans.  Yes,  the  master  of  a  ship  is  in  supreme  control  of  all 
messages  handled  by  the  radio  station. 

63 


64  BADIO  QUESTIONS  AND  ANSWERS 

Ques.  118.     Explain  fully  the  cable  count  system. 

Ans.  The  cable  count  system  of  counting  the  check  is  used 
for  radiograms.  This  system  provides  that  all  words  in  the 
address,  text,  and  signature  must  be  counted  and  charged  for. 

In  this  system  messages  are  divided  into  three  classes,  viz. : 

(a)  Plain  language. 

(b)  Code  language. 

(c)  Cipher  language. 

Plain  Language  messages  must  be  written  entirely  in  plain 
language.  Words  are  counted  on  the  basis  of  fifteen  characters 
to  the  word.  Any  fractional  part  of  fifteen  characters  is  also 
counted  as  one  word.  Numbers  up  to  five  in  a  group  would 
be  counted  as  one  word,  over  five  as  two  words. 

Examples.- 

Gymnasium  1  word  7583         1  word 

Intellectualization  2  words  37463         1  word 

Unconstitutional  2  words         987641         2  words 

Constantinople  1  word 

Code  Language  is  made  up  of  pronounceable  words  of  no 
direct  meaning  not  to  exceed  ten  characters  in  length.  If  a 
code  word  exceeds  ten  characters  in  length  it  is  counted  at 
the  cipher  rate  (5  letters  to  the  word)  and  this  is  noted  in 
the  check.  Non-pronounceable  code  words  are  counted  at  the 
cipher  rate.  Words  in  which  the  meaning  has  been  concealed 
by  reversing  the  order  of  the  letters  or  syllables  will  not  be 
accepted  as  code  words. 
Examples.- 

BEYINXJEHI  1  word 

X-ray  2  words 

XQNOW  Not  accepted — counted  as  cipher. 

Cipher  Language  is  counted  at  the  rate  of  five  letters  to 
the  word  and  may  be  made  up  of  any  combination  of  letters 
or  figures. 


LAWS  AND   TRAFFIC  REGULATIONS  65 

Examples: 

QPWNY  1  word 

QPXNWY  2  words 

A5C  3  words 

"When  a  message  is  written  in  mixed  language  a  careful 
check-up  under  the  following  rules  must  be  made. 

Code  and  Plain  Language.  Maximum  length  of  word 
chargeable  is  ten  characters. 

Plain  Language  and  Cipher.  The  plain  language  is 
charged  at  the  rate  of  one  word  for  every  fifteen  characters 
or  fraction  thereof,  and  the  groups  in  the  passages  in  cipher 
language  at  the  rate  of  one  word  for  every  five  characters 
or  fraction  thereof. 

Plain  Language,  Code  Language  and  Cipher  Language. 
The  words  in  plain  language  and  code  language  are  charged 
as  code  language  and  the  words  in  cipher  are  charged  as 
cipher.  The  word  street,  road,  park,  or  square  is  always 
counted  as  one  word  aside  from  its  designator  in  the  address. 
Hyphenated  or  compound  words  are  counted  as  so  many  sep- 
arate words  depending  on  the  number  of  parts. 

Names  of  places,  such  as  New  York,  New  London,  or  Frank- 
fort Maine,  are  counted  as  one  word  in  the  address  and  two 
words  in  the  text. 

If  New  York  is  written  Newyork  or  New  London  is  written 
Newlondon  and  like  examples,  they  are  counted  as  one  word 
in  the  text  and  so  charged  for.  They  should  be  written  as 
two  separate  words  in  the  address  but  as  the  names  of  all 
cities  count  as  one  word  in  the  address  they  are  charged  for 
as  one  word. 

Ques.  119.  Give  and  explain  twelve  International  abbrevia- 
tions. 

Ans.  Below  is  the  International  List  of  Abbreviations 
which  are  self-explanatory.  Any  twelve  signals  may  be 
chosen.  If  the  three  letter  signal  is  sent  followed  by  a  ques- 


66  RADIO  QUESTIONS  AND  ANSWERS 

tion  mark,  it  refers  to  the  first  column  of  explanation.  If  the 
signal  is  sent  alone  it  refers  to  the  second  column  of  ex- 
planation. See  list  figure  41. 

Ques.  120.  What  are  the  penalties  for  violation  of  the  act 
of  August  13,  1912? 

Ans.  For  violation  of  any  of  the  regulations  of  this  act, 
the  owner  of  the  apparatus  shall  be  liable  to  a  penalty  of  one 
hundred  dollars,  which  may  be  remitted  or  reduced  by  the 
Secretary  of  Commerce.  For  repeated  violations  the  license 
may  be  revoked. 

An  operator  may  be  subject  to  a  penalty  of  twenty-five 
dollars,  which  may  be  reduced  or  remitted  by  the  Secretary 
of  Commerce.  For  repeated  violations  the  license  shall  be 
suspended  or  revoked. 

Ques.  121.  State  the  law  regarding  the  testing  of  a  trans- 
mitter. 

Ans.  The  law  provides  for  testing  as  follows:  Stations 
desiring  to  conduct  tests  should  communicate  with  radio  in- 
spector by  letter  or  telephone,  stating  the  probable  length  of 
time  that  will  be  required.  Stations  conducting  such  tests 
or  temporary  experiments  should  ''listen  in,"  to  determine 
that  no  interference  is  being  caused,  and  during  the  tests 
should  "listen  in"  frequently  for  the  interference  signal, 
"Q.R.M."  Stations  conducting  tests  should  transmit  their 
official  call  signal  frequently.  Attention  is  invited  to  the  act 
of  August  13,  1912,  section  5 : 

"That  every  license  granted  under  the  provisions  of  this  act  for 
the  operation  or  use  of  apparatus  for  radio  communication  shall  pre- 
scribe that  the  operator  thereof  shall  not  willfully  or  maliciously  inter- 
fere with  any  other  radio  communication.  Such  interference  shall  be 
deemed  a  misdemeanor,  and  upon  a  conviction  thereof  the  owner  or 
operator,  or  both,  shall  be  punishable  by  a  fine  not  to  exceed  five 
hundred  dollars  or  imprisonment  for  not  to  exceed  one  year,  or  both. ' ' 


LAWS  AND  TRAFFIC  REGULATIONS 


67 


DEPARTMENT  OF  COMMERCE 

BUREAU  OF  NAVIGATION 


RADIO  SERVICE 


INTERNATIONAL  RADIOTELEGRAPHIC ^CONVENTION 
LIST  OF  ABBREVIATIONS  TO  BE  USED  IN  RADIO  COMMUNICATION 


BBREVI 
AI10N 

QUESTION 

ANSWER  OR  NOTICE 

PRB 

gh 

RC 
RD 

% 
RH 

g 
5? 

RO 

5 

IS 

RV 
KW 

JRX 

IK 

>SA 
ISB 

i 
IS 

SK 

s 

so 

|SP 

1 

su 

sv 

sw 

sx 

SY 

sz 

3 

Do  yon  wish  to  communicate  by  means  of  the 
International  Signal  Code? 
What  ship  or  coast  station  Is  that?  

I  wish  to  communicate  by  means  of  the 
International  Signal  Code. 

My  distance  is.'.'  

W  hat  Is  your  true  bearing?  

Where  are  you  bound  for? 

Where  are  you  bound  from?  .  .  .  .  .  .  ..  .  .  .  .  '.  .  '.  '. 
What  line  do  you  belong  tot  
What  Is  your  ware  length  In  meters?  
How  many  words  have  you  to  sendt  
HoWdo  you  receive  me?  
Are  you  receiving  badly?  Shall  I  send  20?  .  . 

for'adJustmentT  
Arc  you  being  Interfered  with?  
Are  the  atmospherics  strong?  „  
Shall  I  Increase  power?  
Shall  I  decrease  power?  

I'b^^t^r-.v.-.-.'.LW. 

My  wave  length  Is  meters. 
I  have  words  to  send. 

llmrecelvlnf  bldly.    Please  send  20. 

,ambe,n?ln{,r)eWthV- 
Atmospherics  are  very  strong. 
Increase  power. 
Decrease,  power. 
Send  faster. 
Send  slower. 
Stop  sending. 

SSnffisgw 

I  am  busy  (or:  I   am  bnsy  with  ). 
Please  do  not  Interfere. 
Standby.     I  will  call  you  when  required. 
Your  turn  will  be  No  
Your  signals  arc  weak. 
Your  signals  are  strong. 
The  tone  Is  bad. 
The  spark  Is  bad. 
Your  spacing  Is  bad. 

Shall  I  send  slower?  
Shalllstop  sending?  
Have  you  anything  for  me?  

Are  ,«$'•  •••;••::  

Shall  I  stand  by?  
When  will  be  my  turn?  
Are  my  slsnals  weak?  
Are  my  signals  strong?  
ris  my  tone  bad?  ,  

i&ff$?tSJE: 

Is  transmission  to  be  In  alternate  order  or  In 
series? 

Transmission  will  be  In  alternate  order. 

Transmission  will  be  in  series  of  5  message*. 
Transmission  will  be  In  series  of  10  messages. 

The  last  'radiogram  Is  canceled. 
Please  acknowledge. 
My  true  course  Is  degrees. 
I  am  not  In  communication  with  land. 
I    am    In    communication    with  

Infora."5.11.'.'  V.that'i  am  calling  him. 

You  are  being  called  by  
I  will  forward  the  radiogram. 
General  call  to  all  stations. 
Will  call  when  I  have  finished. 

Public  correspondence  Is  being  handled. 
Please  do  not  Interfere. 
Increase  your  spark  frequency.  - 
Decrease  your  spark  frequency. 
Let  us  change  to  the  wave  length  of  

Send  each  word  twice.    I  have  difficulty  in 

RerpeeUVt'hneflastUradIogram.'r 
Your  true  bearing  Is  decrees  from  
Your  position  is....  latitude  ....  longitude. 

'What  rate  'shall'  i'co'l'lect  for.'  .'  .'  .','  .'  '.'.i'  .'  .'  .'  .  . 
Is  the  last  radiogram  canceled  
Did  you  get  my  receipt?  
What  Is  your  true  course?  
Are  you  In  communication  with  land?  
Are  you  In  communication  with  any  ship  or 
station  (or:  with  )? 
Shall  I  inform  that  you  are  calling 

Is  calling  met 

W  111  you  forward  the  radiogram?.  
Have  you  received  the  general  call?  
Please  call  me  when  you  have  finished  (or: 
at  o'clock)? 
Is  public  correspondence  being  handled?  .... 

Shall  I  Increase  my  spark  frequency?  
Khali  I  decrease  my  spark  frequency?  
Shall  I  send  on  a  wave  length  of  
meters? 

Wh'aVls'my  true  bearing?  .'.'.'.i:.'.'.'.:.'.'.'.'.;.'.'.'.; 
What  Is  my  position?...  

•Public  correspondence  is  any  radio  work,  official  or  private,  handled  on  com- 
mercial wave  lengths.  »» 

When  an  abbreviation  is  followed  by  a  mark  of  interrogation,  it  refers  to  the  ques- 
tion indicated  for  that  abbreviation.'  n-swo 

Fig.    41.    International   Abbreviations 


RADIO  QUESTIONS  AND  ANSWEES 


The  Department  holds  that  interference  caused  by  tests  of 
the  character  described  above  is  "willful"  when  no  "listening 
in"  precautions  are  taken  and  the  call  signal  of  the  station 
sending  is  not  repeated  at  intervals. 

Under  certain  conditions  local  radio  inspectors  frame  regu- 
lations to  suit  the  needs  of  a  particular  district.  In  the  New 
York  vicinity,  for  example,  where  the  number  of  testers  is 
very  great,  a  separate  call  signal  is  assigned  to  each  authorized 
tester  and  testing  allowed  only  during  certain  periods  of  the 
hour. 

Ques.  122.    Set  up  a  radiogram  with  a  twelve  word  check. 

Ans.     Example : 

To:  John  Hopkins, 

12  Henry  Avenue, 

Baltimore    (Md.) 

Will   arrive   early   Sunday   morning. 
James. 

NOTE  :  The  name  of  the  state  when  enclosed  in  parenthesis 
is  not  counted  in  the  check  or  charged  for. 

The  abbreviations  listed  below  have  been  put  into  effect  since 
the  original  list  on  page  67  was  compiled. 


Abbrevia- 
tion 

Question 

Answer  or  Notice 

QTB 
QTC 

Are  you  in  accord  with  my  check? 
Please  repeat  first  letter  or  figure 
of  each  counted  word. 

Have  you  anything  to  transmit? 

I  am  not  in  accord  with  you  in  your 
statement  of  the  number  of  words. 
I  repeat  the  first  letter  of  each  word 
and  the  first  figure  of  each  number. 
I   have  something  to  transmit,   or  I 
have    one    or    several    radiograms 
for                                                 

Part  IX 

INFORMATION    REGARDING   GOVERNMENT 
RADIO  LICENSE  EXAMINATION 

After  June  30,  1921,  licenses  to  radio  operators  will  be 
issued  according  to  the  following  regulations.  These  regula- 
tions affect  only  licenses  of  the  commercial  operator.  Licenses 
will  be  ranked  as  to  class  and  grade.  There  will  be  a  first 
class  and  a  second  class.  The  class  certifies  to  an  operator's 
proficiency  as  a  radio  man.  In  addition  to  the  class  the 
licenses  will  also  be  graded  as  first,  second  and  third  grade. 

The  theoretical  passing  mark  will  be  75  per  cent  for  first 
class  and  65  per  cent  for  second  class.  As  far  as  class  is 
concerned  any  person  is  eligible  for  either  the  first  or  second 


The  grade  of  a  license  shows  the  service  an  operator  has 
had.  No  service  is  required  for  the  third  grade,  six  months 
satisfactory  service  is  required  for  second  grade.  Twelve 
months  as  a  second  grade  operator  must  be  had  in  order  to 
be  eligible  for  a  first  grade  license. 

The  code  requirements  are  twelve  words  per  minute  for 
any  second  class  license,  twenty  words  per  minute  for  first 
class,  second  grade,  and  twenty-five  words  per  minute  for 
first  class,  first  grade. 

The  extra  first  class  license  is  issued  by  the  Department 
of  Commerce  to  exceptional  operators  of  good  standing.  The 
requirements  in  code  are  thirty  words  per  minute  Continental 
Morse  and  twenty-five  words  per  minute  American  Morse  (five 
letters  to  the  word).  Satisfactory  service  for  eighteen  months 
during  the  term  of  the  applicant's  unexpired  license  is  re- 
quired. A  theoretical  mark  of  80  or  better  must  be  attained. 


70  BADIO  QUESTIONS  AND  ANSWERS 

Credit  for  the  examination  is  given  on  the  following  basis : 

Points,  maximum  value. 

(a)  Experience    20 

(b)  Diagram  of  receiving  and  transmitting  apparatus 
(fig.  43)    10 

(c)  Knowledge  of  transmitting  apparatus 20 

(d)  Knowledge  of  receiving  apparatus 20 

(e)  Knowledge    of    operation    and    care    of    storage 
batteries   10 

(f )  Knowledge  of  motors  and  generators 10 

(g)  Knowledge  of  Eadio  Eegulations 10 

PLACES  OF  EXAMINATION 

Examination  for  radio  operator's  license  may  be  taken  by 
making  application  to  the  Radio  Inspector  at  any  of  the  fol- 
lowing places: 

Boston,  Mass. 

New  York,  N.  Y. 

Philadelphia,  Pa, 

Norfolk,  Va. 

Charleston,  S.  C. 

New  Orleans,  La. 

Mare  Island,  Calif. 

Puget  Sound,  Wash. 

San  Juan,  P.  E. 

Colon,   Canal  Zone. 

Honolulu,  Hawaii. 

Key  West,  Fla. 

Fort  Omaha,  Nebr. 

Fort  Wood,  N.  Y. 

Fortress  Monroe,  Va. 

Fort  St.  Michael,  Alaska. 

Fort  Valdez,  Alaska. 

Bureau  of  Navigation,  Dept. 
of  Commerce,  Washing- 
ton, D.  C. 


Part  X 
ADDITIONAL  QUESTIONS 

Are  you  well  versed  in  practical  radio?  If  you  are,  here 
are  sixty  questions  you  should  be  able  to  answer.  All  of 
these  questions  are  not  asked  in  license  examinations  and  are 
included  here  for  test  purposes  only. 

1.  Explain  the  construction  of  a  quenched  spark  gap ;  what 
are  its  advantages  and  how  does  it  function  in  a  transmitting 
set? 

2.  Describe  the  relative  advantages  and  disadvantages  of 
damped  and  undamped  waves. 

3.  An  antenna  200  feet  long  and  100  feet  high  inverted  L 
is  erected  on  a  dry  sandy  beach  (soil)  near  seashore.     De- 
scribe a  suitable  ground  for  a  5  K.W.  transmitter. 

4.  Why  is  a  closed  circuit  not  a  good  radiator  of  electric 
waves  ? 

5.  Describe  the  Alexanderson  H.F.  alternator. 

6.  Diagram  of  Lowenstein  \vavechanger. 

7.  Explain  the  theory  and  action  of  a  circuit  breaker  and 
how  to  adjust  it. 

8.  Tell  for  what  uses  series,  shunt,  and  compound  motors 
are  best  adapted.     Give  reasons. 

9.  What  are  interpoles  used  for  on  D.C.  machines? 

10.  Describe  the  types  of  grounds  used  with  sets  operating 
on  sandy  or  dry  ground  and  state  the  advantages  or  disad- 
vantages of  each. 

11.  Describe  the  construction  of  an  induction  coil  or  trans- 
former.   Give  sketch. 

71 


72  RADIO  QUESTIONS  AND  ANSWERS 

12.  Where   are  variable   condensers   used   to    advantage? 
Give  diagram. 

13.  Describe  two  types  of  variable  condensers. 

14.  What   class  of   radiograms  have   precedence  over  all 
others  ? 

15.  Why  are  condensers  sometimes  submerged  in  oil? 

16.  How  do  you  proceed  to  adjust  a  crystal  detector  to 
maximum  sensitiveness? 

17.  Explain  the  difference  between  broad  and  sharp  tuning 
and  advantages  of  each. 

18.  What  is  meant  by  normal  rate  of  charge  of  a  storage 
battery  ? 

19.  What  are  the  causes  of  the  breakdown  of  the  insula- 
tion of  an  antenna? 

20.  How  would  you  test  for  an  open  circuit  in  the  primary 
or  secondary  of  your  induction  coil  or  transformer? 

21.  What  is  advantage  of  cooling  the  spark  gap  by  air 
blast  or  other  means? 

22.  What  is  the  difference  between  A.C.  and  interrupted 
direct  current? 

23.  What  may  be  the  trouble  if  H.W.A.  does  not  register? 

24.  What  is  the  first  thing  to  do  after  receiving  a  message  ? 

25.  Describe  at  least  one  method  of  determining  the  fol- 
lowing antenna  measurements: 

(a)  Fundamental  wavelength, 

(b)  Capacity, 

(c)  Inductance, 

(d)  Resistance. 

26.  In  case  two  or  three  leyden  jars  of  the  main  transmitter 
were  broken  and  having  no  spare  jars,  how  would  you  adjust 
your  transmitter  to  the  original  wavelengths?    What  effects 
would  this  adjustment  have  on  the  coupling? 


ADDITIONAL    QUESTIONS  73 

27.  Describe  an  improved  type  receiver  for  the  reception 
of  undamped  waves.     Make  a  sketch  of  the  circuits  used  in 
the  receiver. 

28.  Draw  an  elementary  diagram  of  the  following: 

(a)  A  magnetic  coupled  receiver  connected  to  a  crystal  de- 
tector for  receiving  damped  waves. 

(b)  A  static  or  capacity  coupled  receiver  connected  to  an 
ultra  audion  for  receiving  undamped  waves. 

In  the  latter  show  a  tickler  coil  connected  in  the  circuit 
and  describe  the  various  parts  that  go  to  make  up  the  circuit 
and  how  the  ultra  audion  enables  you  to  receive  undamped 
waves. 

29:  What  is  the  function  of  a  starting  box  for  a  motor  and 
how  is  it  constructed?  If  one  of  the  steps  of  the  resistance 
burned  out,  how  would  you  temporarily  repair  the  fault? 
Describe  the  action  of  no  voltage  and  overload  devices.  What 
material  should  be  used  for  cleaning  a  commutator? 

30.  If  your  starting  rheostat  burned  out,  what  material 
ordinarily  found  on  shipboard  could  be  used  to  repair  it  tem- 
porarily, to  replace  it,  and  how  would  you  use  this  temporary 
apparatus  ? 

31.  How  are  dynamos  classified  in  respect  to  their  field 
excitation  ? 

32.  Explain  the  difference  between  a  Motor  Generator  and 
a  Dynamo  tor. 

33.  State  in  detail  all  the  factors  that  determine  the  range 
of  a  radio  station. 

34.  Describe  an  arc  transmitter,  giving  a  schematic  dia- 
gram of  the  circuits.    How  does  the  radiation  emitted  by  an 
undamped  wave  transmitter  differ  from  that  emitted  by  a 
spark  system?     Given  a  certain  transmitting  equipment  and 
a  certain  antenna  at  what  wavelengths  will  the  maximum 


74  EADIO  QUESTIONS  AND  ANSWERS 

radiation  be  obtained?     How  will  the  radiation  vary  at  dif- 
ferent wavelengths? 

36.  Name  and  describe  the  most  common  form  of  detector 
for  undamped  waves,  what  are  its  advantages  and  disad- 
vantages ? 

37.  How  may  a  pure  note  be  obtained  in  the  reception  of 
undamped  waves?     Describe  the  construction  and  operation 
of  one  device  for  this  purpose. 

38.  What  is  meant  by  " multiple  discharges"  in  a  radio 
transmitter  ?    What  advantages  are  found  in  this,  and  under 
what  conditions? 

39.  What  is  the  difference  between  trains  of  waves  emitted 
by  the  transmitter  and  the  note  heard  at  the  receiver? 

40.  What  is  the  function  of  an  earth  connection  ?    Describe 
an  efficient  ground  system. 

41.  Describe  the  operation  of  tuning  a  receiver  for  the  re- 
ception of  weak  signals  through  interference.     Do  not  make 
general  statements,  but  describe  in  sequence  and  in  minute 
detail  every  step  of  the  operation  from  start  to  finish,  in  order 
to  obtain  the  best  results. 

42.  What  special  methods  or  devices  are  effective  in  receiv- 
ing through  static,  except  careful  tuning? 

43.  If  the  ship 's  masts  are  destroyed,  how  could  you  arrange 
to  send  and  receive  radio  signals? 

44.  Why  is  special  care  required  in  making  joints  in  antenna 
wire  ?    What  forms  of  coupling  are  used  in  radio  transmitters  ? 
What  are  the  advantages  and  disadvantages  of  each?    How 
can  the  wavelength  of  a  distant  transmitting  station  be  de- 
termined at  the  receiving  station? 

45.  What  simple  test  can  you  apply  to  see  whether  your 
antenna  is  grounded  somewhere  outside  the  building    (sta- 
tion). 


ADDITIONAL   QUESTIONS  75 

46.  How  may  the  amount  of  power  used  in  sending  a  radio- 
gram be  changed? 

47.  What  is  meant  by  the  following:     (a)  A  cumulatively 
compound  wound  motor;  (b)  a  differential  compound  wound 
motor.    Which  type  is  used  for  operating  radio  A.C.  genera- 
tors and  why? 

48.  An  alternator  has  twelve  pole  pieces;  at  what  speed 
must   it  be  run   to   generate  frequency   of   150   cycles   per 
second  ? 

49.  Describe  the  action  of  an  induction  motor. 

50.  How  does  a  single  phase  motor  differ  from  a  three 
phase  motor? 

51.  A  transformer  is  supplied  with  A.C.  at  200  volts  and 
a  frequency  of  60  cycles.    If  it  has  500  times  as  many  turns 
in  the  secondary  as  in  the  primary  what  voltage  will  be  in- 
duced in  the  secondary,  and  how  many  times  will  the  voltage 
rise  per  second  to  a  maximum? 

52.  What  are  the  standard  sizes  of  antenna  wire  in  com- 
mercial service?     What  is  the  tensile  strength? 

53.  What  kind  of  insulators  are  used  for  spreading  the 
antenna  ? 

54.  In  building  a  flat  top  antenna  how  far  apart  would 
you  spread  the  wires? 

55.  Is   it   good   practice   to  solder   the   connection   in   an 
antenna  ? 

56.  How  would  you  count  a  radiogram  composed  of  code, 
plain  language  and  cipher  ?    Would  you  accept  a  paid  service 
message  destined  to  a  ship  at  sea  ?    If  so,  how  would  it  differ 
from  an  ordinary  commercial  radiogram  to  the  same  ship? 

57.  Should  the  number  of  words  shown  in  the  check  of  a 
radiogram  differ  from  the  number  of  words  in  the  message ; 
how  would  you  handle  same  if  the  ship  had  passed  out  of* 
radio  range  ?•  How  long  should  you  hold  an  undelivered  radio- 


76  RADIO  QUESTIONS  AND  ANSWERS 

gram  of  a  commercial  nature  (destined  to  a  ship)  at  a  shore 
station  before  filing  it? 

58.  What  are  the  SVC  messages  ?    Give  the  form  of  a  SVC 
message. 

59.  Give  all  the  requirements  and  limitations  concerning 
relaying  for  both  shore  and  ship  stations.     In  the  case  of  a 
message  originating  on  shipboard,  what  must  be  shown  in 
the  record  of  such  a  message?    In  the  case  of  a  message  re- 
ceived on  shipboard,  what  must  be  shown  on  the  record  of 
such  message? 

60.  Explain  one  theory  of  rectification  by  crystal  detector. 


ELECTRICAL  DEFINITIONS 

Volt:  (1)  Is  the  E.M.F.  induced  in  a  circuit  when  the 
number  of  lines  of  force  linked  with  it  change  at  the  rate  of 
108  per  second. 

(2)  The  E.M.F.  required  to  force  one  ampere  through  a  R 
of  one  ohm. 

Ampere:  (1)  The  amount  of  current  that  when  passed 
through  a  solution  of  silver  nitrate  will  deposit  .001118  grams 
of  silver  per  second. 

(2)  The  amount  of  current  flowing  in  a  circuit  having  a 
resistance  of  one  ohm  at  a  pressure  of  one  volt. 

Ohm:  (1)  The  resistance  offered  to  an  unvarying  current 
by  a  column  of  mercury  at  temperature  of  melting  ice  14.4521 
grams  in  mass  and  106.3  centimeters  long. 

(2)  The  R  of  a  circuit  that  will  pass  one  ampere  at  a  pres- 
sure of  one  volt. 

Coulomb:  The  coulomb  is  the  unit  of  quantity.  It  is  the 
amount  of  electricity  passed  by  one  ampere  in  one  second. 

Joule:  The  joule  is  the  unit  of  quantity.  It  is  the  energy 
expended  by  one  ampere  through  one  ohm. 

Farad :  The  farad  is  the  unit  of  quantity.  It  is  the  capac- 
ity of  a  condenser  charged  to  one  volt  by  one  coulomb  of  elec- 
tricity. 

Watt :  The  watt  is  the  unit  of  power.  It  is  the  work  done 
by  one  joule  per  second. 

Henry:  The  henry  is  the  unit  of  inductance.  It  is  the  in- 
duction in  a  circuit  when  the  E.M.F.  equals  one  volt  while  the 
current  changes  at  the  rate  of  one  ampere  per  second. 

Conductance:  Reciprocal  of  R. 
77 


I 

78  RADIO  QUESTIONS  AND  ANSWERS 

Inductance:  Property  of  a  circuit  that  tends  to  prevent 
any  change  in  the  strength  of  the  current  passing  through  it. 

Reactance:  Reactance  is  due  to  counter  E.M.F.  of  self -in- 
ductance and  is  expressed  in  equivalent  ohms. 

Impedance:  This  is  the  combined  opposition  of  reactance 
and  resistance  to  a  current  in  any  circuit. 

Potential :  When  two  condensers  are  charged  with  electric- 
ity and  they  are  capable  of  giving  off  a  spark  discharge  of 
certain  defined  length.  The  one  giving  the  longest  spark  dis- 
charge in  linear  length  is  said  to  have  been  charged  to  a 
higher  potential. 

Current:  The  term  current  means  the  quantity  of  elec- 
tricity which  passes  in  a  unit  of  time,  and  is  expressed  in 
amperes.  The  current  in  a  circuit  in  inversely  proportional 
to  the  resistance  in  the  circuit. 

Resistance:  The  resistance  of  a  circuit  is  the  property  of 
the  conductor  to  oppose  the  flow  of  the  current.  The  unit  of 
resistance  is  the  ohm  and  is  the  resistance  of  a  column  of  mer- 
cury 14.4521  grams  in  mass  and  106.3  centimeters  long  at  the 
temperature  of  melting  ice.  It  is  the  resistance  in  a  circuit 
when  the  E.M.F.  is  one  volt  and  the  current  one  ampere. 

Capacitance :  The  property  of  a  condenser  by  which  energy 
may  be  stored  up  in  electro-static  form.  The  unit  of  capaci- 
tance is  the  farad  and  is  the  capacity  of  a  condenser  when  it 
is  charged  to  a  potential  of  one  volt  by  one  coulomb  of  elec- 
tricity. 

Inductance :  The  property  of  a  circuit  that  tends  to  oppose 
any  change  in  strength  or  direction  of  E.M.F.  in  an  alternat- 
ing current  circuit.  The  unit  of  inductance  is  the  Henry  and 
is  the  inductance  in  a  circuit  where  the  applied  E.M.F.  is  one 
volt  and  is  changing  at  the  rate  of  one  ampere  per  second. 
Frequency:  The  number  of  times  that  an  alternating  cur- 
rent changes  direction  when  expressed  in  figures;  it  is  the 
number  of  changes  or  cycles  per  second  of  time. 


ELECTRICAL   DEFINITIONS 


Phase :  As  applied  to  alternating  current  denotes  the  angle 
turned  through  by  the  generating  element  reckoned  from  a 
given  instant.  Phase  is  usually  measured  in  degrees  from  the 
initial  point  of  zero  generation. 


Exciting 


^Aperiodic 


Fig.  42.     Measuring  Induction  and  Capacitance  of  Antenna 

Measurement  of  Inductance  and  Capacity  of  Antenna. 
The  fundamental  xf  should  be  carefully  measured  by  use  of 
a  periodic  circuit,  (fig  42)  care  being  taken  that  fundamental  \ 
of  aperiodic  circuit  is  not  close  to  xf.  A  known  inductance 
L!  is  then,  inserted  and  loaded  fundamental,  XL  measured. 
Then 


_  _ 

'" 


C  may  be  found  by  substitution 


BIBLIOGRAPHY 

Text  Books  Suitable  for  Eadio  Students. 

1.  Robison,  "Manual  of  Radio  Telegraphy  and  Telephony." 

2.  Stone,  "Elements  of   Radio  Telegraphy." 

3.  Fleming,  "Elementary  Manual  of  Radio  Telegraphy  and  Radio 
Telephony. ' ' 

4.  Bucher,  "Practical  Wireless  Telegraphy." 

5.  Hayward,  "How  to  Become  a  Radio  Operator." 

6.  U.  8.  Signal  Corps,  "Radio." 

7.  Stanley,   "Wireless   Telegraphy." 

8.  Goldsmith,  "Radio  Telephony." 

9.  Bangay,  "The  Elementary  Principles  of  Wireless  Telegraphy," 
volume  I  and  II. 

10.    Lauer  and  Brown,  "Principles   of  Radio  Engineering." 

ARC  TRANSMITTERS 

1.  Manual  for  Radio  Operators 

Published  by  Federal  Telegraph  Company 

2.  Robinson's  Manual  for  Naval  Electricians 

U.   S.  Naval  Institute,  Annapolis,   Md. 

3.  I.  R.  E.  Proceedings;  Volume  5  No.  4,  P.  O.  Pedersen, 

"On  the  Poulsen  Arc  and  its  Theory";  Volume  7,  No.  5,  L.  F. 
Fuller  "The  Design  of  Poulsen  Arc  Converter  for  Radio  Tele- 
graphy"; Volume  9,  No.  3,  P.  O.  Pedersen  "On  the  Poulsen  Arc 
in  Coupled  Circuits." 

4.  Bucher,  "Practical  Wireless   Telegraphy." 

STORAGE  BATTERIES 

1.  Croft  "Practical  Electricity." 

2.  U.  S.  Signal  Corps  "Radio." 

3.  Pamphlets  published  by  the  Electric  Storage  Battery  Company, 
Philadelphia,  Pa. 

4.  Pamphlets  published  by  the  Edison  Storage  Battery  Company, 
Orange,  New  Jersey. 

5.  Bucher,  "Practical  Wireless  Telegraphy." 


BIBLIOGRAPHY  81 

GENERAL  ELECTRICITY 

1.  Croft,  "Practical  Electricity." 

2.  Swoope,  "Lessons  in  Practical  Electricity." 

3.  Timbie,  "Essentials  of  Electricity." 

VACUUM  TUBES 

1.  Lauer  and  Brown,  "Principles  of  Radio  Engineering." 

2.  Bucher,  "Vacuum  Tubes." 

3.  I.   R.  E.  Proceedings;  Volume  2,  No.  1,  "The  Audion  Detector 
and    Amplifier";    Volume    5,    No.    2,    "A    Study    of    Hetrodyne 
Amplification  by  the  Electron  Kelay";   Volume  5,  No.  6,  "The 
Manufacture  of  Vacuum  Tube  Detectors." 

4.  Lodge,  "Electrons." 

RADIO  LAWS  AND  REGULATIONS 

1.  U.  S.  Eadio  Regulations 

Superintendent  of  Documents,  Government  Printing  Office,  Wash- 
ington, D.  C. 

2.  Commercial  Traffic  Regulation 

Superintendent  of  Documents,  Government  Printing  Office,  Wash- 
ington, D.  0. 


APPENDIX  I 

The  Chemistry  of  the  Edison  Storage  Battery.  The  fun- 
damental principle  of  the  Edison  Storage  Battery  is  the  oxi- 
dation and  reduction  of  metals  in  an  electrolyte  which  neither 
combines  with  nor  dissolves  either  the  metals  or  their  oxides. 
Also,  an  electrolyte  which,  notwithstanding  its  decomposition 
by  the  action  of  the  battery,  is  immediately  re-formed  in  equal 
quantity,  and  is,  therefore,  a  practically  constant  element 
without  change  of  density  or  conductivity  over  long  periods 
of  time.  Therefore,  only  a  small  quantity  of  such  electrolyte 
is  necessary,  permitting  a  very  close  proximity  of  the  plates. 
Furthermore,  it  is  unnecessary  to  take  hydrometer  readings 
until  about  three  hundred  cycles  of  charge  and  discharge 
have  been  made ;  this  is  simply  to  determine  when  it  is  neces- 
sary to  empty  out  the  old  solution  and  put  in  new.  The  ac- 
tive materials  of  the  electrodes  being  insoluble  in  the  electro- 
lyte, no  chemical  deterioration  takes  place  therefrom. 

The  chemical  reactions  in  charging  the  Edison  Storage 
Battery  are,  (1)  the  oxidation  from  a  lower  to  a  higher  ox- 
ide of  nickel  in  the  positive  plate,  and  (2)  the  reduction  from 
ferrous  oxide  to  metallic  iron  in  the  negative  plate.  The  oxi- 
dation and  reduction  are  performed  by  the  oxygen  and  hy- 
drogen set  free  at  the  respective  poles  by  the  electrolytic  de- 
composition of  water  during  the  charge.  The  charging  of  the 
positive  plate  is,  therefore,  simply  a  process  of  increasing  the 
proportion  of  oxygen  to  nickel.  The  proportions  of  nickel  to 
oxygen  in  definite  oxides  of  nickel  are  as  follows: 


APPENDIX  I  83 

Atomic     Proportions      By  Weight 

Ni  O  Ni  O 

MO  1  1  1  .273 

Ni,O4  1  1.33  1  .364 

Ni:O3  1  1.5  1  .409 

NiO2  12  1  .545 

The  relative  amounts  of  oxygen  necessary  to  oxidize  nick- 
elous  oxide,  or  NiO,  which  is  the  oxide  corresponding  to  the 
green  nickel  hydrate  used  in  making  the  battery,  to  the  vari- 
ous oxides  are  given  in  the  three  reactions : 

(1)  6  NiO  +  20  =  2  Ni,04 

(2)  6  NiO +  30  =  3  Ni2O3 

(3)  6  NiO +  60  =  6  NiO2 

The  Ni02  is  capable  of  reacting  with  NiO  according  to 
the  reaction  Ni02  -f-  NiO  =  Ni203.  Ni304  is  considered  as  a 
combination  of  NiO  -f-  Ni203  =  Ni304. 

From  a  chemical  standpoint  a  charged  condition  of  the  cell 
would,  therefore,  be  represented  in  the  positive  plate  by  an 
atomic  ratio  of  nickel  to  oxygen  of  at  least  1:1.5  (or  Ni203), 
depending  on  the  charge.  A  discharged  condition  would  be 
represented  by  a  ratio  of  1 :1.33  (Ni304)  or  lower,  depending 
on  the  discharge. 

The  discharge  of  the  cell  is  simply  the  reversal  of  the  above 
reactions,  the  hydrogen  reducing  the  higher  oxides  of  nickel 
to  lower  oxides  and  the  oxygen  oxidizing  the  iron  to  ferrous 
oxide. 


APPENDIX  II. 
THE   CARE   OF  BALL  BEARINGS* 

LUBRICATION.  As  these  machines  cannot  always  be 
placed  on  ship-board  with  the  shaft  fore  and  aft,  there  may 
be  times  when  they  will  be  subjected  to  severe  rolling  and  it 
is,  therefore,  desirable  in  general  to  use  a  medium  grade  of 
grease  similar  to  No.  3  Keystone  grease  which  is  made  by  the 
Keystone  Lubricating  Company  of  Philadelphia,  Pa.  A  slight- 
ly lighter  grease  could  be  used  in  cold  weather  or  where  there 
would  not  be  much  rolling.  Any  similar  good  grade  of  grease 
would  be  satisfactory  but  it  must  be  absolutely  neutral  or  test 
free  from  acid  or  alkali. 

The  other  important  requirement  is  that  the  grease  must 
contain  no  fibrous  material  and  must  withstand  a  tempera- 
ture of  100  degrees  C  or  higher  without  any  material  change 
in  its  consistency  when  cold.  Some  greases,  upon  being 
heated,  separate  into  a  thin  oil  and  a  relatively  viscous  soapy 
material.  This  kind  of  a  grease  should  not  be  used  unless  ab- 
solutely necessary.  If  the  bearings  are  filled  full  of  grease 
it  will  be  found  that  a  portion  of  this  will,  after  running  for 
a  time,  work  out  of  the  ends  of  the  bearings,  leaving,  how- 
ever, sufficient  to  properly  lubricate  same.  After  operating 
for  a  month  or  so  it  is  desirable  to  thoroughly  flush  out  the 
bearings  with  gasoline  or  kerosene  oil  and  fill  with  a  good 
grease.  After  this,  if  the  bearings  are  kept  free  from  all  dirt, 
grit,  etc.,  they  should  not  need  cleaning  and  refilling  with 
grease  more  often  than  every  six  months. 

•From  directions  published  by  Crocker- Wheeler  Co. 
84 


APPENDIX  II  85 

CLEANLINESS.  This  is  an  extremely  important  mat- 
ter with  ball  bearings  and,  therefore,  all  foreign  material  ex- 
cept the  grease  must  be  carefully  excluded.  Care  must  be 
taken  that  no  dirt  or  grit  of  any  kind  is  carried  into  the  bear- 
ing with  the  new  grease,  or  otherwise,  when,  for  any  reason, 
the  bearing  caps  are  removed. 


RADIO  QUESTIONS  AXD  AXSWEES 


rnis  BOOK  is  uu-h;  r>"  tne  lar* 


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